I uninstalled MW, deleted the AppData/Roaming/MediaMonkey-map, let CCleaner do his register-job, restarted my PC and reinstalled MW. Everything is works fine now...

You could try to rename the Scripts folder to Scripts-off in the MediaMonkey install folder, start MediaMonkey, use and change Now Playing and use File > Exit. Then see if on the next start the Now Playing has been retained.

Is there a better way to correct this, than to reinstall MW?

BTW, MW doesnt do this on my laptop, where I have the songs as well (synced by Synology).

That means MediaMonkey isn't shutting down properly. Only when you exit MediaMonkey properly is the Now Playing saved. If you are closing MediaMonkey it may be an Addon that is causing MediaMonkey not to shut down properly.

Dear,

Every time when I (re)start MW 4.1.19.1859, it keeps using an older playlist of (deleted) songs. Yes indeed, it is an dominant playlist, because it doenst show the previous playlist that I was listing to the last time. Even when I try to use this older playlist, MW cannot find all of these songs, including those who are still in the library.

In my chase that means that I have to select every time the songs I would like to hear, and adding them to the playlist (select > [ALt+Enter]).

It is worth noticing, that I keeps all my songs on my Synology DSM 216+ II, but MW is installed on an updated W10-64b.