Folders in sidebar

[lstell]

In the middle screenshot at the top of the README (https://github.com/mbnuqw/sidebery/blob/v5/docs/assets/screenshot-005.png), tabs are organized in folders and there is a new folder icon to the right of the new tab button below the list of tabs. How do I get these features? Putting tabs into groups does not affect the sidebar.

I am using version 5.3.3 in Firefox 139.0.1 (aarch64) on OSX. I have also tried using the development version and tried it in my Ubuntu virtual machine.

[lstell]

I've mostly answered my own question. If one right clicks on a tab (or set of selected tabs) in the sidebar, there is a Group entry in the context menu. There are also a couple of relevant entries in the Tabs portion of the Keybindings in Settings. I still don't know how to get the New Folder icon that is shown in the screenshot mentioned in my original posting, but I can make do without it.