With the exception of the user profile set-up, which is not an acceptable option, neither this suggested solution, nor any of the others I’ve seen in this thread seem to work for me. (Windows 11, LO 18.104.22.168 (x64)
My situation, a two-monitor configuration, presents a slightly different challenge. Upon accidental undocking, the sidebar appeared on the adjacent, much smaller screen (positioned somewhat lower), with the title bar and any menus now being off-screen, above the upper screen border. So there is (using Windows 11, and probably same on Windows 10) no way to grab that sidebar and move it, nor can any main menu options be seen or actuated. That sidebar cannot be moved by pointing the cursor at just any gray space, clicking, holding and dragging. Seems like you can only drag it by clicking and holding the title bar (which is normal, in Microsoft Windows). But, when cursor will stop at the edge of the the screen, there’s no way to even blindly find and grab that title bar. Nor does the typical method of recovering off-screen windows work, since, being a sidebar, it is not treated as a regular window, and will therefore not show up as something that can be moved, when hovering over the Calc icon in the Windows Task Bar in order to pop up the Move Window option. Alt-Tabbing won’t list it either.