In fact I did it just like you recommeded. And it worked out fine.
The difficulties I ran into (see post #17) were due to the fact that I run thunderbird in a firejail sandbox by default.
Of course just running the process thunderbird wouldn´t locate its new profile location as the TB profile settings (defined by firejail) are too restrictive to access it.
As already pointed out the command I´d have to use is:
I missed that you are using thunderbird with firejail. If I had, I’d not have posted because I know nearly nothing about using it (firejail). I’m very happy you found a proper fix to help resolve your limited /home storage space issue.
Best luck with everything you do in the future and if I can help, I’ll be very happy to try,