I was always annoyed that in linux renoise version you have to always change focus from a plugin window to DAW window if you want to play a few notes and see how it sounds.
So I made a very simple script that uses xdotool to solve this issue. It basically waits for focus change events and as soon as one happens, it switches focus back to the renoise window.
You can just download it, put it into ~/bin or ~/.local/bin or /usr/local/bin depending on your distro and personal preferences, make it executable with chmod +x and use
permafocus.sh start to fix the focus at currently focused window,
permafocus.sh stop to stop it and
permafocus.sh toggle to, well, toggle it.
You might have to install xdotool to use it.
Suggested use would be to use your window manager or hotkey daemon to bind this script to some key combination. I personally use win+s to toggle permafocus.
I hope this is helpful to somebody here.