Auto-Matte in OSX across multiple frames in the time-line

Hi there, just to check this can be done on OSX as well as Windows as I can’t find the shortcut. I could press Alt-Shift in Windows and select multiple frames in the timeline once I had my layer chosen to be able to generate an auto-matte across a multiple frames. However, can’t find the same shortcut in OSX - tried all combinations of shift, command, option and control. Any clues? Thanks in advance.

It’d be the same shortcut as selecting multiple layers of a scene across multiple frames. This might be related to an issue I’m having in SBPro/Harmony with the rotate canvas tool not working - it disappears when the pen gets near when pressing the shortcut.