Excellent, because it's not only a way to open OR to switch to the Gmail tab (it's very useful when it's already open to avoid opening several Gmail tabs, by using the addon icon, and it opens as a pinned tab, that's a great idea.). It's also a Gmail badge counting the unread messages. The check messages every X minutes is great.

The feature that is missing for me, is to count new messages from now (because I've some messages that I've let unread in Gmail on purpose, like spam, or for other reasons). Customizing the unread badge would be a great idea also. It's too small.

so simple yet so helpful

I loved GMail Panel... (and other add-ons that are no longer available with the new firefox)
I use now "Waterfox" a forked version of Firefox where old add-ons are still working.

Is there a way to find the previous version of Gmail Panel ?

The checker option doesn't work

На иконке с конвертом Gmail не отображается кол-во новых писем. В итоге плагин просто закрепляет иконку Gmail в любое место окна браузера. С таким же успехом я могу просто закрепить вкладку и периодически на нее переходить.

the epoch has left. it's not that addon anymore :(