Hi Stef,
we are providing all airports in the MSFS2020 which we can update due our data provider. So, beta or not beta, but you should use all airports - specially LSZH which is a major airport (at least in my Austrian eyes :-)).
I guess, you have more a mess in your scenery file. So please try the following first (and please follow EXACTLY all steps in the correct order):
This should re-ordering your content-scenery file after that all ICAOs should be usable.
Cheers,
Richard
PS: my assumption is, that you use no addon-linker, sorter or similar else …