It should be possible to auto-generate these block editing UI's starting from an abstract description of the syntax, as used e.g. in a tree-sitter parser. Sometimes this kind of block-based editing is also integrated with type checking to enable smart, query-based filling of "holes", as seen perhaps most prominently in editors for Agda (a pure functional language).
Yeah, we actually took that approach for the block-based experiment for Khan Academy. I think we ran into issues with auto generating the blocks for JS prototype based classes, if I recall correctly, but I can't remember exactly what the issues were. I don't know what approach OP is using.
