Hi
I'm currently working on a tutorial video showing how layers work in the Hema app. The layers work as expected, and yes, the percentage slider is not there in Hema Explorer. This feature was removed mainly because A) Most people (in our limited tests) don't use it, a B) It caused many bugs & unfavorable performance issues, especially in lower-end Android devices that don't process maps very well.
The short answer on using layers:
"Active" layers will try to 'load' or 'cache' all the tiles for active layers into the map. ONLY the top layer will show if the tiles for that layer & zoom are loaded (either from the device or from the cloud). The way I use active layers is this:
I load 2 or 3 layers into the active area, and quickly switch between them for route planning, since no single layer has all the data I need.
When I'm tracking, I generally only keep 1 layer active. This results in better performance and I hardly ever see missing tiles since I always download & verify my tile downloads before leaving data service.
"Available" layers are just that...layers that can be added to the active menu. If a layer is in the "Available" area, the system will not try to load/cache tiles for that layer.
I hope this helps...it's not confusing for the thousands of people new to the platform, but for those that are used to having the percentage slider, it can take a little getting used to