Swap cookies от Cimbali

Manage several sets of cookies so you can login simultaneously with several accounts to any website. To switch between accounts, just select the right cookie profile you created and named, the tabs on that website will refresh automatically.

The Swap cookies icon opens a window with a drop-down list of cookies and some buttons:
- Select the desired cookie profile in the list and click "Select" to use it
- Select "New batch of cookies" and click "Select" to start a new profile
- To rename a profile, select it, enter the new name in the text box below and then click "Rename to"
- To delete a profile, select it, and click the "Delete" button. The profile must not be in use (or be the last saved profile for this site).

Note that Firefox Multi-Account Containers is a more fully-featured and stable alternative to this add-on.