In the Activity tab for a contact, case activities are not shown. I would rather they were...
Me too! And After a lengthy process I've had this PR 1630 merged into core, should be released in 5.24 I think.
It adds an option (Administer » CiviCase » CiviCase Settings) that, if checked, will include case activities in the activities tab (and other activities ...
I dont think you can add source contact in profile field and do a bulk update. The options i can think of
Run sql query to update contact_id in civicrm_activity_contact table for record_type_id = source.
Or Export the activities you want to update and import them back with adding source contact id column in the csv file.
If the activity relates to the Case, then create it there but otherwise just on the Contact.
For example, if you have a case for managing volunteer onboarding, then a meeting relating to onboarding would be a case activity but a phone call about a donation would be a simple contact activity.
Kate, Welcome to CiviCRM stack exchange. About your question, it depends upon your business logic. If you want the activity to be part of the case than you should create them inside a case since the New Activity form from the Contact summary page doesn't provide ability to add activity to case. You can but obvious move the activity later after creating by ...