There's a discussion of the issues here: https://support.mozilla.org/en-US/questions/1079688 I've never tried what you are attempting but it doesn't seem to be recommended.

Thanks for the link. It shows that others have tried to achieve a similar setup. The info regarding different operating systems is helpful and interesting. I had been trying to achieve a local folder network link from Thunderbird on a PC running Linux mint, but without success. I have since found that a Windows 7 laptop and a Windows 10 laptop can both achieve same Thunderbird Local Folder storage on my networked NAS drive. Though after reading the note you linked to, I've avoided using both at the same time. Maybe swapping the PC from Linux Mint to Windows is a future option. Thanks again.