Allow Admin to choose different default by Activity type record

We have a user request for an Activity type to have a different type of default value from a custom Dropdown data category which is used across all activity record types and is sync back to Salesforce. 

When creating a Timeline activity, we would like to be able to set different default value in a custom field for each activity type. e.g User is working on two timeline activity, a “Call” activity with a custom default session value “Reactive” and “Email” activity with a custom default session value “Proactive.” Both activities using same custom field “session type” but different default values.