This issue is referenced in source/tests.

The list includes:

• Order of events raised by CompileMethod
• Normalize whitespaces (PR)
• AssociatedExtensionImplementation should work on constructed symbols (currently only definitions) Extensions: AssociatedExtensionImplementation on constructed symbols #80423
• Fix SymbolDisplay with UseMetadataMemberNames on extension symbol Extensions: DocumentationCommentId and ExtensionGroupingName/ExtensionMarkerName APIs, update grouping type metadata name #80164
• Test IOperation on various usages of extension members (should show in instance form with a receiver, with extension rather than implementation symbol)
• Test GetSpeculativeSymbolInfo
• Test IsAccessible
• Improve handling of BoundBadExpression in GetMemberGroup (see PreferMoreSpecific_Static_MethodAndProperty, PreferMoreSpecific_Static_MethodAndProperty_Generic, TwoExtensions_MethodAndProperty)
• Fix arity in symbol display for VB Extensions: DocumentationCommentId and ExtensionGroupingName/ExtensionMarkerName APIs, update grouping type metadata name #80164

There are more APIs we could add or APIs we could enhance, but we can wait until the IDE or other customers say they need it:

• ReduceExtensionMember Need way to check if a particular (modern) extension member is applicable to a receiver type. #80273
• New API to pair symbols for FAR? (similar to TryGetCorrespondingExtensionImplementationMethod) (PR)
• Should the GetMemberGroup API be adapted for the new scenario where a property access could refer to one of multiple properties?
• we need a public API for ExtensionName to support symbol display in VB (PR)
• LookupStaticMembers should return extension static members

Relates to test plan #76130