Are you aware only global variables can be watched?

So whats the correct method to debug then? Doesn't seem too user friendly

You could write the interesting variables to the output log.
And watch them in realtime. (Thus also local variables)

I never use a debugger.

How do I do that? Did a search in the manual and nothing comes up

Same here, never used the debug run. I only use DEBUG_VAR, draw_quad, draw_text, beep, diag_var and diag.

As said you can use the draw text, or popup windows for showing realtime data. (printf)

What gamestudio is missing (since I know it) is a propper
output to the commandline, or a debug multiline logger.

Its in demand for years.

You can help yourself by using a customly written Log viewer.

@Superku, Damocles: Same here. The debugger is so useless executing code with it takes longer than doing good guesses and using print_whatever functions. The fact that SED crashes when the program crashes doesn't make it more usefull. ^^

The watch area only read global variables, if you need a local variable you must create a global variable, like var ASD;, then, where the local variable is write "ASD = local_variable;", and finally put the watch to ASD

That is pretty error prone as multiple instances of functions can run in the same frame. I wouldn't recommend this technique.

Ok I added 2 global variables (e.g. outside of the function)
var STARTX;
var STARTY;
I then have this in the function:
STARTX = iGenerateStart_X;
STARTY = iGenerateStart_Y;
I then added a watch for both STARTX and STARTY, start in debug mode, step through each line... nothing... it says "Not Available"