Container Cookie Switcher od Lucky

Container Account Switcher gives you a one-click popup for switching between multiple accounts on the same website — no digging through Firefox's container submenu.

How it works
Each account you add gets its own real Firefox container (a separate, permanent cookie jar). Click the toolbar icon on any site to see your saved accounts for that domain. Click one and it jumps straight to that account's tab if it's already open, or opens the site fresh in that account's container if not.

Because each account's session lives in its own untouched container the whole time, switching never triggers login rotation, session invalidation, or logout — a problem that affects any tool that tries to copy/replay cookies into a single shared browser profile.

Features

One click to switch, or jump to an already-open tab for that account
New account creates a fresh, permanent container and opens the site in it
Colored dot per account, "open" tag when a tab is already active
Delete an account slot (and its container/cookies) when you're done with it