The current version 5.4.8(446) do not support tags in sub folders, apparently stuck in the layer time period. The tags in folders are suddenly losing their parent folder designations and are lost in an alphabetical list.
For the short term, you could set up scenes in the web or desktop version, and use those to quickly flip through the desired tag visibility combinations in the mobile viewer, that will help, at least. But an update is appropriate, last update was 6month ago. Before then, there was a monthly update…