Back in the day I owned a couple Atari ST, I used a cartridge based program for writing video games. It was called "ACTION" Does anyone remember this program or even better, know where I can get a ROM dump for my emulator?
For the Atari 8-bit, not the Atari ST, everything you've asked for (and more can be) found at the Action page at AtariWiki.
Action! is a programming language for the Atari 8-bit line. It was never ported to the Atari ST.
I can't find a ROM of the cartridge, but the Internet Archive does hold printed manuals for the language as well as its source code, which was released under the GPL by Action! author Clinton Parker.
- Manual (2018 edition): https://archive.org/details/ActionManual3rdRevisedEdition2018ByGBXL
- Source code: https://archive.org/details/ActionVersion36_SourceCode