Hello ​@Johannes Rott, 

There is no such feature available in Mews.
We have raised this feature request several times in our conversations with Mews.
In the feedback portal, there is a similar feature request, and I have posted a comment in that thread specifically requesting exactly what you are asking for.

Please vote for the request and add any comments you feel are relevant. 
https://feedback.mews.com/forums/955598-guest-experience/suggestions/45278224-product-restrictions

​@Robin Gustavsson did the same. would allow us gaining more revenue. i will let the CPTO i have spoken to know as well. maybe it speeds the procedure a bit up.