If you need to check out a particular license to all users (for example an Office 365 license, which every user in your organization should theoretically have) or bulk checkin a license from all users (for example if you stopped using G-Suite), there is a console command to let you do that:

snipeit:checkout-to-all {--license_id=} {--notify}

and

snipeit:checkin-from-all {--license_id=} {--notify}

The --license_id is the ID number of the license you'd like to check in or out. If you'd like to send the normal notifications that would be sent on checkin and checkout, use the --notify flag.