Multi Account Containers Isolation

Open new Temporary Containers if a Permanent Container Tab tries to load a Domain that isn't assigned to "Always open in" that container

Enabled: If you have the Multi-Account Containers Add-on installed then it's only possible to load URLs in Permanent Containers whose Domain is assigned to Always open in in Multi-Account Containers. Subdomains can't be matched and will also get isolated.

Note: To add new sites to permanent containers with MAC you need to disable this configuration temporarly, or use the toolbar icon popup to disable Isolation globally (circle icon), which makes assigning new sites easier. You can enable the popup in the general preferences.