Great to see you like CSV2STOS, I enjoyed updating it lately!
Regarding extensions, I would say that both Misty & Missing Link are essential. They both complement each other. A Misty command is used within one of the Missing Link's programs funnily enough. Stevie Wonder has some nice commands too, for blitter copying and the STE sound side of things.
TOME is fun to explore but optional these days, not essential. Missing link maps are faster and basically M.L. succeeded TOME later down the track. You can actually convert Amiga TOME maps with CSV2STOS too. It doesn't look like the map format changed, I tried a few of them and they all worked.
It came about because I was experimenting one day to see if I could get CSV data out of old TOME maps to convert them, and I succeeded. Later I realised I could add/merge the code into CSVSTOS, mainly to help out any old timers who might still have older TOME maps kept from many years back. So then they would be able to convert their maps into Tiled *.TMX map format by hacking a "dummy map" within Notepad, obviously set up to the correct size (with a corresponding tile bank set up within the dummy map too). The idea was that then you could convert these maps back into Missing Link world or landscape maps, or you could proceed to use the same map for producing a "remake" with another modern language/engine perhaps.
The same thing happened concerning AGT maps, I was tinkering with AGTCUT.EXE to see what it could do. Then that converter code got merged in too!
You are interested more in the Falcon 030 and TT side of things from the sounds of it? I would still recommend exploring Control extension, Extra extension, also Neil Halliday's GBP extension and STORM development extensions because there's handy commands within all of them.
If you use Visual Studio Code, you can download the STOS VSC plugin from their store page which Neil put together. This allows you to code without line numbers then compile to an *.ASC file. It's really useful. Combined with Tiled and CSV2STOS, your workflow can speed up quite dramatically.
More info here on what to do:
https://stoscoders.com/visual-studio-code