9c2787c1_he_Beat__A_Blog_by_PremiumBeat__Description
[Command] Add marker Add marker/modify Delete marker [Shortcut] m Option+m Control+m [UI Icon] N/A [Description] 
Adds a marker at the location of the skimmer or playhead. To edit the marker’s text, press m again, or press Option+m to add and modify.
Final Cut Pro X Shortcuts - The Big Cheat Sheet - The Beat: A Blog by PremiumBeat
Description