I wan’t to have a simple menu (main menu not menu bar) whith buttons to link to another form(s)/window(s)/caveses(s). Or atleast the code to switch bettween the screen.

What code (SQL/PL) would I put in the buttons or is there a better way to do this?
That’s a very broad question. If you want to show a specific window on
WHEN-BUTTON-PRESSEDthen you can use built in like below-The above would work if you use the
SET_WINDOW_PROPERTYwithin the same form.In case you want to call another form from the parent form (which is the case as per your comment screenshot) you need to to use
CALL_FORMbuilt-in like