diff --git a/pcbnew/drc/rule_editor/drc_re_custom_rule_panel.cpp b/pcbnew/drc/rule_editor/drc_re_custom_rule_panel.cpp
index 6fe4b9d517..d7c0e81b04 100644
--- a/pcbnew/drc/rule_editor/drc_re_custom_rule_panel.cpp
+++ b/pcbnew/drc/rule_editor/drc_re_custom_rule_panel.cpp
@@ -23,7 +23,11 @@
 
 #include "drc_re_custom_rule_panel.h"
 
+#include <stack>
+
+#include <scintilla_tricks.h>
 #include <wx/sizer.h>
+#include <wx/stc/stc.h>
 
 DRC_RE_CUSTOM_RULE_PANEL::DRC_RE_CUSTOM_RULE_PANEL(
         wxWindow* aParent, std::shared_ptr<DRC_RE_CUSTOM_RULE_CONSTRAINT_DATA> aConstraintData ) :
@@ -34,22 +38,47 @@ DRC_RE_CUSTOM_RULE_PANEL::DRC_RE_CUSTOM_RULE_PANEL(
     m_textCtrl = new wxStyledTextCtrl( this, wxID_ANY );
     sizer->Add( m_textCtrl, 1, wxEXPAND | wxALL, 5 );
     SetSizer( sizer );
+
+    m_scintillaTricks = std::make_unique<SCINTILLA_TRICKS>(
+            m_textCtrl, wxT( "()" ), false,
+            // onAcceptFn
+            []( wxKeyEvent& aEvent )
+            {
+                aEvent.Skip();
+            },
+            // onCharFn
+            [this]( wxStyledTextEvent& aEvent )
+            {
+                onScintillaCharAdded( aEvent );
+            } );
+
+    m_textCtrl->AutoCompSetSeparator( '|' );
 }
 
+
+DRC_RE_CUSTOM_RULE_PANEL::~DRC_RE_CUSTOM_RULE_PANEL()
+{
+}
+
+
 bool DRC_RE_CUSTOM_RULE_PANEL::TransferDataToWindow()
 {
     if( m_constraintData )
         m_textCtrl->SetValue( m_constraintData->GetRuleText() );
+
     return true;
 }
 
+
 bool DRC_RE_CUSTOM_RULE_PANEL::TransferDataFromWindow()
 {
     if( m_constraintData )
         m_constraintData->SetRuleText( m_textCtrl->GetValue() );
+
     return true;
 }
 
+
 bool DRC_RE_CUSTOM_RULE_PANEL::ValidateInputs( int* aErrorCount, std::string* aValidationMessage )
 {
     (void) aErrorCount;
@@ -70,3 +99,156 @@ wxString DRC_RE_CUSTOM_RULE_PANEL::GenerateRule( const RULE_GENERATION_CONTEXT&
 
     return wxEmptyString;
 }
+
+
+void DRC_RE_CUSTOM_RULE_PANEL::onScintillaCharAdded( wxStyledTextEvent& aEvent )
+{
+    if( aEvent.GetModifiers() == wxMOD_CONTROL && aEvent.GetKey() == ' ' )
+    {
+        // Short-cut for do-auto-complete
+    }
+
+    m_textCtrl->SearchAnchor();
+
+    wxString rules = m_textCtrl->GetText();
+    int      currentPos = m_textCtrl->GetCurrentPos();
+    int      startPos = 0;
+
+    enum class EXPR_CONTEXT_T : int
+    {
+        NONE,
+        STRING,
+        SEXPR_OPEN,
+        SEXPR_TOKEN,
+    };
+
+    std::stack<wxString> sexprs;
+    wxString             partial;
+    EXPR_CONTEXT_T       context = EXPR_CONTEXT_T::NONE;
+
+    for( int i = startPos; i < currentPos; ++i )
+    {
+        wxChar c = m_textCtrl->GetCharAt( i );
+
+        if( c == '\\' )
+        {
+            i++; // skip escaped char
+        }
+        else if( context == EXPR_CONTEXT_T::STRING )
+        {
+            if( c == '"' )
+                context = EXPR_CONTEXT_T::NONE;
+        }
+        else if( c == '"' )
+        {
+            partial = wxEmptyString;
+            context = EXPR_CONTEXT_T::STRING;
+        }
+        else if( c == '(' )
+        {
+            if( context == EXPR_CONTEXT_T::SEXPR_OPEN && !partial.IsEmpty() )
+            {
+                m_textCtrl->AutoCompCancel();
+                sexprs.push( partial );
+            }
+
+            partial = wxEmptyString;
+            context = EXPR_CONTEXT_T::SEXPR_OPEN;
+        }
+        else if( c == ')' )
+        {
+            if( !sexprs.empty() )
+                sexprs.pop();
+
+            context = EXPR_CONTEXT_T::NONE;
+        }
+        else if( c == ' ' )
+        {
+            if( context == EXPR_CONTEXT_T::SEXPR_OPEN && !partial.IsEmpty() )
+            {
+                m_textCtrl->AutoCompCancel();
+                sexprs.push( partial );
+                context = EXPR_CONTEXT_T::SEXPR_TOKEN;
+                partial = wxEmptyString;
+                continue;
+            }
+
+            context = EXPR_CONTEXT_T::NONE;
+        }
+        else
+        {
+            partial += c;
+        }
+    }
+
+    wxString tokens;
+
+    if( context == EXPR_CONTEXT_T::SEXPR_OPEN )
+    {
+        if( sexprs.empty() )
+        {
+            // Top level - suggest (rule or (version
+            tokens = wxT( "rule|version" );
+        }
+        else if( sexprs.top() == wxT( "rule" ) )
+        {
+            // Inside (rule ...) - suggest sub-expressions
+            tokens = wxT( "condition|constraint|layer|severity" );
+        }
+        else if( sexprs.top() == wxT( "constraint" ) )
+        {
+            // Inside (constraint ...) - suggest constraint parameters
+            tokens = wxT( "min|max|opt" );
+        }
+    }
+    else if( context == EXPR_CONTEXT_T::SEXPR_TOKEN )
+    {
+        if( !sexprs.empty() && sexprs.top() == wxT( "constraint" ) )
+        {
+            // After (constraint - suggest constraint types
+            tokens = wxT( "annular_width|"
+                          "assertion|"
+                          "clearance|"
+                          "connection_width|"
+                          "courtyard_clearance|"
+                          "creepage|"
+                          "diff_pair_gap|"
+                          "diff_pair_uncoupled|"
+                          "disallow|"
+                          "edge_clearance|"
+                          "hole_clearance|"
+                          "hole_size|"
+                          "hole_to_hole|"
+                          "length|"
+                          "max_error|"
+                          "min_resolved_spokes|"
+                          "physical_clearance|"
+                          "physical_hole_clearance|"
+                          "silk_clearance|"
+                          "skew|"
+                          "text_height|"
+                          "text_thickness|"
+                          "thermal_relief_gap|"
+                          "thermal_spoke_width|"
+                          "track_angle|"
+                          "track_segment_length|"
+                          "track_width|"
+                          "via_count|"
+                          "via_diameter|"
+                          "zone_connection" );
+        }
+        else if( !sexprs.empty() && sexprs.top() == wxT( "layer" ) )
+        {
+            // After (layer - suggest layer keywords
+            tokens = wxT( "inner|outer" );
+        }
+        else if( !sexprs.empty() && sexprs.top() == wxT( "severity" ) )
+        {
+            // After (severity - suggest severity levels
+            tokens = wxT( "error|warning|ignore|exclusion" );
+        }
+    }
+
+    if( !tokens.IsEmpty() )
+        m_scintillaTricks->DoAutocomplete( partial, wxSplit( tokens, '|' ) );
+}
diff --git a/pcbnew/drc/rule_editor/drc_re_custom_rule_panel.h b/pcbnew/drc/rule_editor/drc_re_custom_rule_panel.h
index 4e2be18b12..05b49e6e01 100644
--- a/pcbnew/drc/rule_editor/drc_re_custom_rule_panel.h
+++ b/pcbnew/drc/rule_editor/drc_re_custom_rule_panel.h
@@ -24,12 +24,16 @@
 #ifndef DRC_RE_CUSTOM_RULE_PANEL_H
 #define DRC_RE_CUSTOM_RULE_PANEL_H
 
+#include <memory>
+
 #include <wx/panel.h>
 #include <wx/stc/stc.h>
 
 #include "drc_re_content_panel_base.h"
 #include "drc_re_custom_rule_constraint_data.h"
 
+class SCINTILLA_TRICKS;
+
 /**
  * Simple panel used for editing custom rule text.  The panel consists of a
  * single wxStyledTextCtrl allowing free-form rule entry.
@@ -38,7 +42,7 @@ class DRC_RE_CUSTOM_RULE_PANEL : public wxPanel, public DRC_RULE_EDITOR_CONTENT_
 {
 public:
     DRC_RE_CUSTOM_RULE_PANEL( wxWindow* aParent, std::shared_ptr<DRC_RE_CUSTOM_RULE_CONSTRAINT_DATA> aConstraintData );
-    ~DRC_RE_CUSTOM_RULE_PANEL() override = default;
+    ~DRC_RE_CUSTOM_RULE_PANEL() override;
 
     bool TransferDataToWindow() override;
     bool TransferDataFromWindow() override;
@@ -47,8 +51,11 @@ public:
     wxString GenerateRule( const RULE_GENERATION_CONTEXT& aContext ) override;
 
 private:
+    void onScintillaCharAdded( wxStyledTextEvent& aEvent );
+
     std::shared_ptr<DRC_RE_CUSTOM_RULE_CONSTRAINT_DATA> m_constraintData;
     wxStyledTextCtrl*                                   m_textCtrl;
+    std::unique_ptr<SCINTILLA_TRICKS>                   m_scintillaTricks;
 };
 
 #endif // DRC_RE_CUSTOM_RULE_PANEL_H