Many accounts for major sites/workspaces now span multiple subdomains of the same site, or even different domains, as well as many SSO and authentication flows becoming more popular, which all adds up to many potential login URLs that would relate to the same username & password.
Having to maintain login info for the same account in multiple entries in password manager is labor intensive and introduces risk (forgot to update manually in all locations).
The Firefox Password Manager needs a mechanism to link the same account to multiple sites.
One way to help with this would be to setup 'Equivalent Domains': ideally a global list (to simplify known subdomains using the same account credentials for basic users) which can be modified by advanced users to add known equivalents (see Manage Equivalent Domains in Account Settings from LastPass Guide).
Another idea would just be to allow adding secondary URLs to an existing password entry, with the same logic to resolve/simplify the URL to subdomain level, as used for the initial entry.
Thanks for your consideration!