Mouse/Touchscreen

[tunagenes]

I think this answer from @riban to a different question might help:

Official RBPi TouchScreen 7"

Hi @tunagenes! There have been some enhancements to the touch interface with the quantity of onscreen buttons minimised to provide more screen for display of the UI. As has (almost) always been the case, the top left of the screen (where you see “Main” on you screenshot) acts as a hidden touchpad / button. It generally acts as the BACK button but a bold press will show the menu. Most screens can be navigated / controlled using the touch interface. If you have onscreen buttons enabled then extra…

and it also points to a wiki entry that has more info.