Try clicking on the blue gem for the Group window (DarqUI settings), then go to the Settings tab. Change the 'Layout Mode' to something different, then set it back to the one you want. This should reset all the buttons. It will also show you where the buttons are, since they can be in several different arrangements.
If you created a custom layout, I have no idea. You could try moving the cure blocks, saving it, then moving them back and saving again.
Just don't click the Other tab - there's nothing there, and all the tabs disappear when you do. The dropdown appears at the top, but Group isn't listed. If you hit Other, and you aren't finished, you'll have to close the Settings window and use your Group window to re-open it.