If you would like to control the splash screen procedurally, you need to know the splash screen's window reference number. To get the number, you need to create an on startup method like this:

C_LONGINT(<>SScreen)
<>SScreen:=Frontmost window

Once you have the reference number you can apply it to other commands like:
SET WINDOW RECT (left; top; right; bottom{; window}) `Resize the splash screen
HIDE WINDOW {(window)} `Hide the splash screen
SHOW WINDOW {(window)} `Show the splash screen
MINIMIZE WINDOW {(window)}`Restore the splash screen
MAXIMIZE WINDOW {(window)}`maximize the splash screen