I’m sure you already noticed that the active build configuration is the checked one when looking at the drop-down list of the “hammer” build button in the toolbar.
But since it didn’t seem clear enough (after all, maybe you didn’t noticed it…), we already made an enhancement in 1.1.2 to add a visual decorator to the active build configuration output folder.
Just for you, a confidential sneak peek of the 1.1.2 project explorer
While this is definitely an improvement, I would prefer something a bit more like you get in visual studio. The toolbar indication is preferable, because it is always visible. The target output folders in the project explorer often get pushed off the bottom of the screen, so are not clearly visible.