- download the bat file
- put it into the same directory with firefox.exe
- run the bat file
- you can now notice a new profile is launched in the same directory
- if you wish, check official document to migrate data from your previous profile
- if you don't wanna bother asking each time:
- open the bat file in any text editor
- delete contents despite the last line
- change the variant
profileName
into the profile folder name you prefer