Second, I don't really know if I should call this a bug, or a lack of support from the game itself.
I'm playing with a 2560x1080 resolution, and...
There's a mod in the workshop that solves this problem about 21:9 resolutions with the vanilla UI. I know this is probably way down in your priority list, but I wonder if there's some kind of fix in your plans, or maybe some config file I can edit myself. I lost count how mane times I've misclicked by now.
Thanks for your time!