I am sharing a webmap with everyone but it contains part of layers shared with a specific group.
As a result, a user not belonging to that group receives requests to identify himself by user name/password.
Is there a way to suppress those requests and just not to show the layers?
Typically people use two apps. One with the secure layers and one without. A secured layer will always prompt for access. It is possible that a persons token could have expired and then the prompt would be valid. Excluding it would prevent that workflow, which is equally valid. My guess is that you could handle this in a bespoke app, but I doubt you can in a template/builder for the token-expiry reason above.