Global variable (creation / Update / Reading) - Ideal tyre temperature

Hello,

I created (using some elements of some Dahsboards) a Dashboarb intended for an old IPAD.

The games I own range from Assetto Corsa (1st of the name) to Le Mans Ultimate.

The problem encountered is the lack of information from the games to have an ideal target temperature of the tyres (as a result, the information displayed is truncated).

So I would like to be able to manually set a target temperature and to do this I think I will go through a global variable that I can update using 2 buttons (plus and minus).

Does anyone know how to create/read/update a global variable (the ideal would be to be able to update it from another Dashboard).

Thank you.