...
FOLIO community documentation for Check in out includes the permissions required to interact with the app, and that determine what you can or cannot do within the app.
You can assign permissions to users in the Users app. If none of these permissions are assigned to a user, then they will be unable to see the Check in out app or any related information.
...
Note: A patron must first be assigned as a proxy for the borrower in their user record in the Users app.
In the Who are you acting as? dialog, select the name of the user they will be acting as a proxy for and click Continue. The Who are you acting as? dialog closes and patron and proxy details are displayed.
...
By default, the Check out session is configured to end automatically after a 3 minute period of inactivity. You can turn this setting off or edit the number of minutes of inactivity the session will end after in the Settings app.
See the FOLIO community documentation here.