If you want to get some flavor of what editing on the Canon Cat may have felt like, especially the LEAP keys, try Jasper and/or bitters.

Jasper:

https://lab.alexanderobenauer.com/jasper/

https://lab.alexanderobenauer.com/updates/the-jasper-report

bitters:

https://m15o.ichi.city/bitters/

https://nightfall.city/nex/in/m15o/projects/bitters/ (very similar to the link above, but Nex is a neat protocol...)

https://sr.ht/~m15o/bitters/

Furthermore, Internet Archive hosts a runnable Canon Cat Emulation. I believe this means it is available in MAME as well.

https://archive.org/details/canoncat