What is the best way to install a beta release in parallel to the stable release version, while making the licensing and the navdata(base) work?

Should I just copy the publicbeta executable of the download into the same pilot2atc folder, or should I create a separate folder of some kind?

What I now tried is to make a copy of the complete 2020 stable folder, renamed it to 2021, and installed the beta version into that one. One of the points to watch out is, to not install into another subfolder (this happened to me before). Also the installed has created a desktop shortcut with the 2020 in the name, which I needed to manually rename.

Not sure, whether this the correct way, but so far it seems to work in terms of license and navdata.

I just keep the stable version and current beta downloads and just install over top.  This will preserve your settings and especially the taximnt database.  Nothing wrong with what you are doing but you will lose settings and I am not sure it helps as the common point is what is located in your appdata and doesn't understand stable or beta.

If it works great.

I have GB of chatter sound files, etc and I am always running beta.  Old problems fixed and new problems arise but these days new problem are not that bad really.  Then there is airac data to keep up to date.

This is one problem that just installing the version you want to use today is simple and takes little time.

Happy flying

Do I understand this right, that installing over the top will still allow my to run the older stable version, if I chose do to so, just be starting the other executable? Does the "installing over" not also overwrite some files of the stable release version so that is gone for good?

Having the Release and Beta versions in completely separate folders is a good way to go.  You can name the folders whatever you like and then just be sure the installer installs to those folders as it will get confused with multiple installations to different folders.

Dave