1) to show only a specific measurement use the left menu, choosing the measurement you want on the screen, this measurement will be "added" to the bottom bar on the screen; depending on the font size, you can have 4 or less measurements at the same time on the screen
2) you can clear the line with the right menu "clear"
3) if I understood correctly, you want to remove "measure all": you can do it using the right menu and pushing on "measure all"
I suggest to watch some YouTube reviews and you will understand quickly many menu commands and functions of the scope.
Hope it helps