From what I remember, this would require DMT to install a DLL to handle this and I wanted to keep the install process simple, so decided against implementing this or at least until I fond a simpler way to implement it. A quick search found another open source program 'SpecialK' (https://github.com/SpecialKO/SpecialK) which does seem offer this functionality along with lots of other features for gamers. I have not tried this program myself, but it may offer what you want.
Your idea would work if all of your monitors have different target names, but if you have 2 or more monitors of the same type, then it will not be possible to uniquely identify them.
Sorry, but the only thing that I can think of is that you have something else running that keeps changing the windows settings.
Release 2.12
V2.12 - Update to indicate latest version
2.12
No. Currently only one key out of left-control, right-control, left-shift and right-shift can be specified, although you can also use a mouse button. Is there any particular reason why you would want to be able to use either control key?
clean up ready for 2.12