After settings migration from jedit 4 to 5, xinsert clip library is empty. I copied the clips to the old location and they are visible again.
XInsert establishes proper configuration directory for its clips at the first run. Then the directory location is saved in settings and available through plugin options. So it seems like the user needs to change the directory in plugin options manually after switching from jedit 4 to 5.
This regards Windows only. One can see what is the new settings directory through jEdit menu: Utilities / Settings Directory.
This workaround should be acceptable. No automatic solution is planned for XInsert plugin.