You can always add more members to your Trackingplan account. For it, just click on Settings & Members and copy and paste the emails of the users you want to add.
You can also specify the roles of these new users. Specifically, there are three different roles that allow users varying permissions in your Trackingplan account:
The Admin role allows team members to make changes to the workspace settings and preferences, invite new members, and edit the tracking plan. Admins are also the only members who can remove other members from the team.
The Editor role allows team members to make edits to the tracking plan but does not allow them to edit the workspace settings and preferences. Editors also cannot invite new members to the workspace.
The Viewer role allows team members to view the tracking plan only. They can’t make any edits or invite new members.