Hi LakeMonster
Using Non-default Add-ons in Tor Browser is strongly recommend against.
The Tor Project explicitly warns against using non-default add-ons with Tor Browser:
However, the only add-ons that have been tested for use with Tor Browser are those included by default. Installing any other browser add-ons may break functionality in Tor Browser or cause more serious problems that affect your privacy and security. It is strongly discouraged to install additional add-ons, and the Tor Project will not offer support for these configurations.
https://whonix.org/wiki/Tor_Browser#Unsafe_Tor_Browser_Habits
https://whonix.orgwiki/Tor_Browser#Non-default_Add-ons
Recommend: Find a open-source password manager that stores passwords locally
Related:
https://forums.whonix.org/t/add-password-manager-by-default/189