How to add an external team member during modelling phase

To add a collaborator in a template during contract modelling phase select the Collaboration Tab, here you can search for a member to add.
The member can be part of your team or an external member, who you can invite.

When you add a new member to the template you can also assign him a role. If he is an external member he cannot have a manager role, but if the member is part of your team, you can select him as a manager in the template.

You can also edit the role during the modeling process and remove the member.