So, in most web browsers, tabs are placed at the very top of the screen, as many users are used to just moving your mouse to the top to switch quickly. A few browsers however, like Opera and Vivaldi, by default, have a small space on top of the tabs, so you have to click on the tabs more precisely (that CAN be turned off, though.)

As for Groupy, you can do this with the "Always place above" option BUT not with the "Combine if possible" option, as, for some reason, switching doesn't work by clicking at the top-most pixel, so you have to go a few pixels below to actually be able to click on the tab.

I may have an idea as to why this happens, but in any case, is this something that can be fixed, or is it a windows thing that sadly can't be fixed?