Sven got it !
"he opens up the editor from within PM, edits the picture in one of the mentioned image applications, saves and overwrites the file and when returning back to PM the old preview (before editing) is still displayed."
When returning back to PM after treating my photo from preview, it's still on preview mode, so I'm obliged to quit manually this mode to return to the contact sheet. In the former version, the contact sheet was automatically displayed, which was more convenient.
Bests regards
PS : written by my daughter !