During the creation of a new app, we experienced another issue.
In the draft view of the app, we can choose all employees in the employee column. However, as soon as we are in the App view, only one employee (not myself) is chooseable.
All employees of the current project are already signed to a role in the User and role management of the universal app and should by design be able to be edited.
Selecting other users in universal apps does not supported currently. Currently, only users that already presented in some records the current user can see can be selected.
In most cases, an app user should not see other users to avoid data leak (think that you are building a custom portal app).
We have a plan to let the app builder to specify which collaborators be loaded and can be selected in a later version.