My customers are asking for improvements in the authentication of the WVD App

For the reboot issue, if the user is assigned to a personal desktop and given the right permissions, they should be able to reboot the VM from within the session. We don't currently have an option in the client to remotely reboot the PC without being connected to it. And as David mentioned, you don't generally want users rebooting multi-session VMs.

For the credentials, the client doesn't save the credentials, it's standard behavior for Azure AD. We are working on an option to prompt for credentials every time which may help with this. Otherwise, when the signs out of the subscription, it should clear the user as expected. If they are using a public device, they really should be signing out.