There are couple of improvements in user experience for sub grids and form tab in Power Apps Mobile app.
Check other blog posts on Release 2020 Wave 2
- Headers are more protruding for sub grid to separate it from rest of the sections of the form.
- There is also an option (+ New Case – below) to add new record inline for empty sub grids.
- Commands on sub grid opens as a drawer from the bottom of the screen.
- Form tabs can be scrolled horizontally and selecting the tab automatically adjusts the header.
Hope it helps..