Is there a built-in Q&A? If not, then one thing might be to explicitly ask for suggestions from attendees afterwards. For instance I’m sure among the audience there will be real experts in UI and in plenty of other areas. Some of them can probably give you quite valuable feedback about your application design.
Perhaps before the conference ends, you can also round up some novice users to use your application without you guiding them about what to do, so you can see any difficulties the users might have using your application. I’m curious to know if a novice user can easily distinguish the three layer-related toolbar buttons from the other toolbar buttons, given they’re neither grouped together nor apart from the rest.