Ok, i m back to Station 
So, this is what i can get…
1/ choose to add a new “LIST” (not just a Field Imput) for Subcat Name. (within the MAIN cat frame)
2/ maybe you did not chose the “current Subcat” …so as to get ONLY the 1 to 1 Corresponding Subcat Value.
3 / do NOT use MaxRec 1… My bad… 
I have just heard today that React Nativ relies a lot on Nested component… so that is the way to think of when doing that kind of stuff
Maybe you d want to support this component REQUEST for a practical compact Data Display 
Compact GRID 2x2 to 5x5