Thank you for your post!
This behavior isn't new to FileMaker 15 software, older versions also behaved this way. No tick mark shows to the left of the Folder that contains the Current Layout. You might add this as a suggestion in the Product Ideas Space.
I am also going to move this thread from the FileMaker Community Feedback Space, which is specifically for input on the Community itself, to the Discussions Space where you should receive even more views and potentially more advice!