This has been added in the latest update.
Go to ‘Invite volunteers’ via either of the two locations here:
In addition to the already existing option of sending an invitation via Restarters.net, you can now also click ‘Invite via shareable link’:
You can then copy and paste the link in the ‘Shareable link’ into an email that you send to volunteers, or into a social media post:
When clicking on the link, volunteers who already have an account on Restarters.net will be automatically added to your group (if they are logged in - if not, they will be prompted to log in). Volunteers who do not have an account yet will be taken to the registration page - once they have completed their registration they will automatically be added to the group.
The same process also works for invitations to RSVP to an event.