xfce4-places-plugin not finding recent documents

I am running Linux Mint 19.3 with xfce. Some time ago I changed the file manager from Thunar to Nemo, and installed the xfce4-places-plugin. Everything worked fine and I could access recent documents via the places plugin. Then I changed back from Nemo to Thunar, using the "preferred applications app". When I then opened files with Thunar, they did not show up in the "Recent Documents" pop-up list in Places. I suspected that the places-plugin did not automatically change its settings to Thunar, so I uninstalled the xfce4-places-plugin, then reinstalled the places-plugin, but the problem persisted. Whenever I opened a file in Thunar, it did not show up in "Recent Documents" pop-up list in Places, but when I opened it with Nemo, it did so. So I uninstalled Nemo, uninstalled the places-plugin, uninstalled also teh xfce4 Panel, then reinstalled the Panel plugin, and the Places plugin, but the problem is still there: no recent documents are shown in Places when I open them with Thunar. -- Thanks for any ideas how to fix this.

P.S.: The reason I changed back from Nemo to Thunar is that the "Recently used" files folder in Nemo displayed every day a lot of files that I actually did not open for many weeks. That's another story I would like to understand.