How to have multiple entries for custom entity?

Question

In our Dynamics CRM online custom project - we\'ve the default ACTIVITIES tab in a custom entity named DocProject\'s form

Answer 1

In order to have the associated activity grid like the one in the DocProject entity, you need to enable the option Activities when you're creating the entity (this option can't be changed after the entity is created). This option will create the association with the activities entities and allow you to track all the related phone calls, task, etc.

I think that the problem that you're having is that you defined the DocProjectActivities as an activity entity and therefore you can't have this kind of relationship with the other activities entities. I recommend you to take a look to the differences between Entities and Activity Entities.