There are 2 repositories under structure-editor topic.
Don't let the cursor slow you down
A list of projectional and structural editors
A projectional editor for JSON DSLs
Intentional human-machine interfacing through fusion of (keyboard-driven) syntax-based editing and ladder typing.
PoC collaborative, structural programming combination of IDE, OOP language, and VCS. Currently in planning and experimenting stage.
Structure editor for a basic typed functional programming language