You could give a try to the add-on "Quick Folder Key Navigation" https://addons.thunderbird.net/en-US/thunderbird/addon/quick-folder-key-navigation/

Here are a few various options depending upon what you are trying to achieve. If you know the name of folder and want to see all emails in that folder: via 'Menu Bar' Toolbar * Edit > Find > Search Messages * Search for messages in: choose folder name on the account. * 'To' 'begins with' and type first part of your email address * click on search It should show all contents of the desired folder. If you want to locate all folders that only contain eg: 'unread' mail: * In 'Folder Pane Header' * click on the far right 3 dot icon > Folder Modes > select 'Unread Folders' They will show as a block of folders in Folder Pane. They may get added to the bottom of the Folder Pane, but you can move it to the top * Locate 'Unread Folders' block and click on 3 dot icon and select 'Move up' If you frequently use or are currently wanting to work on a small group of folders, you can set them up as 'Favourite Folders' : Right click on folder and select 'Favourite folder' * In 'Folder Pane Header' * click on the far right 3 dot icon > Folder Modes > select 'Favourite Folders' This saves you from having to keep scrolling to locate them. There is also an addon which may work for you - please note addon extensions are maintained by the author and not Thunderbird. * https://addons.thunderbird.net/en-GB/thunderbird/addon/quick-folder-key-navigation/ How to install an addon: * https://support.mozilla.org/en-US/kb/installing-addon-thunderbird

Thank you all for what you need, the problem is solved!