The Firefox Container feature lets you define a container that visits to a particular site will always open in (e.g. open all LinkedIn pages in a particular container to keep them isolated from other sites).
LastPass allows you to have multiple login credentials for the same site.
But at the moment, if you want to open multiple containers so you can simultaneously log in to multiple accounts at the same site, you have to manually open the containers and enter the url to each, before filling credentials with LastPass. It would be great if you LastPass could signal to Firefox to open a particular named Container for a particular login credential.
(I don't know if it is technically feasible but if it is it would be a great feature)
[I am thinking of this in the context of DNA testing sites where you might have different login credentials for each member of the family]