All I want to say is Thank You, the developers and community.
I came to forums to ask if there was a way to do exactly this sort of thing. And I found this thread.
Stupid me, I have completely forgotten, that DisplayFusion let's you code your own functions, in c# no less (my favorite language). Now that I think about it, I remember it was one if not the most important things that I liked, when I bought the software. Or rather I was deciding, if I want to try it out, because I have bought and went through the most of the popular monitor managers over the years and I was tired of switching and learning ins and outs of another one, all over again. But when I saw custom functions in c#, I remember buying right then and there. The funny thing is, I was probably busy to play with it straight away, so I didn't. And then I completely forgot about it.
Anyway. What can I say more: although it's was the first time of me messing with it - it took me all but 10 minutes. Downloaded both scripts from the Keith and DS. using them as example, just made the changes to suit me. DS, thanks for the colors - very nice and very handy to differentiate between the "groups" of functions, and the "close" functionality.
Between that, and the most user-friendly "in-built" scripting GUI, with the debugger (verify), in 10 minutes I had exactly what I came here for and works like a charm.
Once again, to the devs of DisplayFusion - thank You. I have many times used DisplayFusion as an example of superb software at an awesome price and with very reasonable licence options. Now I feel, like I have even better reasons for keep using it it as an example, for how software should be done and priced. Kudos!