Second, add-ons and theme isn’t saying exactly “extensions”. Also, it would take you to the last tab which is by default plug-ins. try it.

You can click the Extensions toolbar icon that was added by default for everyone a bit ago, and at the bottom of the list of your extensions it has a "Manage Extensions" option (it is actually pinned to the bottom of the visible menu, so even if you have enough extensions that it "overflows" into a scroll menu, the Manage Extensions button is always visible). That page lets you remove / configure any currently installed extensions, and has a search bar for the Extensions store as well.