if a macro is altered by another user while the macro edit window is open, it cannot save the changed macro.

to repeat:

• open 2 browsers
• in b1 open a macro, change a few things
• in b2 open the same macro, change something
• in b1 save the macro
• in b2 attempt to save the macro, observe the save fails silently

we might imagine a little warning banner which tells you that the macro cannot be saved.