You can set up a template to include 'Form Submission' triggers that are linked to forms on your template.  When you make a new campaign using this template, the forms in the 'Landing Pages' folder will not appear in the triggers setup immediately.  This is because they have not been published.

Edit the forms, save them and publish them, they will then show in the drop down for the 'Form Submission' trigger.

If you are creating or editing a trigger, and find that there are no forms to select in the drop down, first edit the form in question, save it, then publish it.  It will now appear in the drop down.

If you find that they are still not appearing, reach out to your CSM or raise a support ticket.

For more frequently asked questions on triggers, see the below article:

https://support.vutu.re/hc/en-us/articles/360020699858-Triggers-FAQs