It’s something that I’ve been doing for 10+years, but every couple of years I need to configure this again (on a new machine), and then I need to look it up because I forgot the details. Hence this quickpost.

This is how I run Firefox on Windows:

"C:\Program Files\Mozilla Firefox\firefox.exe" -ProfileManager -no-remote

This allow me to run multiple instances (option -no-remote) of Firefox and invoke the profile manager to select the desired profile at startup

Quickpost info