you should be able to just bind a key to swap to a specific window, no?
i use F8 through F12 and ALT+F8 through ALT+F12 to swap to my windows (10box).
im not using ISboxer though. but it should also have the same "bind key" to any function, no?
i know this isnt 100% what you asked for.
but if you want something that custom, isboxer might not be able to do it, you'd have to script it.
in HKN you can just setup a panel of overlay buttons at any screen coordinate you want. any size you want. any color/transparency you want etc.
then you make those overlay buttons behave however you want them to.
you could swap window on mouseover, left-click, right-click, thumb-button-click, shift+left-click, ctrl+right-click.....mouseover+hotkey.....whatever you want.
something like this?
i did it messy. in 2 mins. my math is off with the pixel positions and labels but no matter.
dont think i'll use this, but interesting idea.
i tested it out swapping windows with middle mouse button.
i have a healer clicker setup like this that activates / deactivates with a key toggle (caps lock).