I often wonder what sort of tools like this must have existed in-house at the many small game development studios of the era.

This one reminds me of another modern compiler for the Intellivision console called INTYBasic, which has an extremely impressive suite of games and NES remakes implemented in it:

https://nanochess.org/intybasic.html

https://youtu.be/h7ttNz2UVw8

For something even higher level check out GBStudio:

https://www.gbstudio.dev/