Forcing windows onto specific monitors

[archaeometrist]

I'm running a Dell system using 18.04LTS, with dual monitors and using 4 workspaces. It works well, but there is one thing I would really like to find out how to do.

I always set up my 'starting programs" on Workspace 1, with Firefox on my left monitor and Thunderbird on the right. I also have a small program, "twclock" set up to show on all the active Workspaces, with it always on top (set to GMT). Depending on what I'm doing, I use the other workspaces, with each assigned a category (such as analysis/journal articles/files).

I would like to set up my system so when it boots, Firefox is on my left monitor and Thunderbird on the right, with twclock as described. Is there a way to do this which is relatively simple (in Gnome)?

If so, how?

I've tried CCSM, but no matter what I do there, it doesn't make the proper changes.

Thanks!
Bob

[archaeometrist]

I need to add - I've also got Gnome-Tweaks, but it does nothing like what I need.