Admin Access for Webform Entries The following problem has occurred: 
A client fills in a reservation form, but the time requested is already fully booked. The clerk and the client negotiate a different time, and the clerk wants to change the requested time (f.e. 18:00) to the negotiated time (f.e. 20:00) -- but as the same form has a date restriction (one cannot reserve on the same day) the clerk can't save the form at the day of the appearance. 

Is there any way to give a role the permission to change every webform, without any restrictions? I.e. any changes made by role "Trusted User" will not be checked in any way.
Webform for Drupal 8 allows you to give a role (or specific user) access to view and update submissions of a SPECIFIC webform to accomplish what you need

Goto Settings > Access of the webform in question and assign VIEW ANY SUBMISSIONS and  UPDATE ANY SUBMISSIONS to your Trusted user role



Than you have to give this user the URL to view and edit/update all the submissions.  For example for the contact form they should visit /admin/structure/webform/manage/CONTACT/results/submissions and they would be able to see all submissions and edit them.