Why can't I link an activity in my Matter Template?
Matter Template events and tasks can be linked to create cascading activities.
If you are unable to link a Parent activity to an event or task, it is likely that your Parent activity has not yet been designated as a Milestone.
Designating your event or activity as a Milestone will enable other activities to be linked.
Here is how to edit an event or task so that they are 'linkable':