I have shortcuts for Picard, mp3tag and Beets as external tools. For Picard and mp3tag, multiple selected files open in a single instance of the application.
Beets, being command line, requires that I have a string to open Powershell, then pass the <path> field to beets.
I just had a moment where I triggered the hotkey for the slot that is assigned to Beets by accident, and it tried to open 1500 Powershell/Beets instances at once which brought my machine to its knees.
My request is that Musicbee just not run a given external tool if a user-defined limit of selected files is exceeded, or that it detect that what are effectively repeats of the exact same command are being run; The web link tools do not open 15 tabs when I use my google link for an album when I have all its tracks selected.