Do a Google on scripter compile error h - quite a few hits on this forum come up, in particular one long thread from 2018. It seems to be some kind of problem with the visual basic interpreter, possibly interacting with particular character combinations in the code. There seem to be two fixes - one is to make sure you are running the latest Mach version, I think that's .062. The other is to open the macro in the operator/edit VB macro menu, then select save as, and save as compiled code (.mcc).
To single step, open the code in the VB scripter window as above (before compiling I think), you will see a row of icons just below the menu bar. The green right arrow runs the macro, the green one with two green bars immediately after it is the single step. If you hover your cursor over each icon its function is shown after a second or so.