Bad Parallels 26 Update Experience from latest 25.x

[AndreasK27]

I updated to Parallels Dektop 26 Pro (have Pro subscriptions) on my M4 Pro MacBook Pro, running Sequoia 15.6.1. The update went very fast, but it then "forgot" the Parallels configuration entirely and acted very weirdly:

1. I had to re-activate my license (OK, easy but unnecessary and a bit complicated, because I needed to find the right subscription/key for this Mac, I have multiple).
2. What I then got was the "Install Windows" dialogue and could not get out of it easily - no Control Center!
3. Luckily I could get out of this behavior via drag&drop of my VMs from my Parallels folder.

VERY BAD experience! Especially when you are traveling like me, think it is a minor update (its dialogue did not look differently to me from the normal minor ones), and have to do a VM-demo later.
I'm posting this, so that you don't panic like me, when/if this happens to you.