As a default, users can access all the forms of the helpdesk. It is possible to show a specific form only to a specific group (of users). Here are the steps:
First, (if you don't have one already) you'll need to create a group for this user(s). You can do this by going to `Admin Settings -> Users`. Look for your user, and then click on the pencil icon to edit the user's profile. Click on create group.
Once you have the user in a group, you'll need to create a queue only for this group. You can do that in `Admin Settings -> Queues and Emails`, and then click on +new queue.
Next, you'll need to go back to your the form you want to share only with this group. That's in `Admin Settings -> Ticket Forms`. Click on Edit Form Fields. Edit the Queue field, and choose your newly created queue. Make sure to not show this field to the user. Click Save.
Lastly, we'll need to edit Queue Access Rights. That can be found in `Admin Settings -> Queue Access Rights`. We'll need to update the group access so that this special queue can only be accessed by your special group.