I apparently accidentally deleted the “Recent Documents” list, and now I cannot find an important and complicated document among my hundreds of documents in many folders and subfolders. Isn’t there a way to restore the Recent Documents" list? And if not, a way is sorely needed.
What about the list in the taskbar?

I don’t think that’s possible.
You can use your file manager to search for a known file.
Search (in Windows -Explorer) for all .odt-files, then sort this list (right mouse-button > context menu) by date.