Updated after developer's response:
I use Panorama Tab Groups add-on which breaks tabs into groups. The Firefox original list button opens up a list of tubs in the active group, which is convenient. Yours, instead, shows all the tabs including the hidden, which makes no sence.

If you consider updating the add-on to match tab grouping, I would be happy to use it.

Is it possible to add an option to let users chose the icon theme to be same as original tab list button?

This is cool.
Sidebar is not cool.
But I request the installation of an optional switch to prevent auto-closing and close button.
Because I want to use this as a pseudo-sidebar.

Very nice highly-customizable extension, must have for efficient tab management and switching between them. List loads pretty fast and opens in the popup, which is so useful and user-friendly. Icon is displaying tab count number Using it for one or two years already, I like to see it developing and improving with each version!

Here are some of my suggestions:
1. The thing extension lacks is the ability to discard or freeze tabs, still need to use other addons for freeing resources (mem, cpu) consumed by tabs. That would be highly appreciated as tab list already displays inactive and loaded tabs as grey and black titles.
2. Would like to change tab count number, two-rows icons&font colors&sizes as well.
3. Option for action buttons to be displayed only when the cursor howers above each tabs line.

Where can I send any other ideas or questions?

Thanks for developing this!

Nice addon. Could you consider adding a searchbar and allowing users to select multiple tabs to do operations on all those selected tabs?