One a normal incident/change_request or task form (wherever Activity Stream is used), we see either "Show one journal field" or "Show all journal fields" buttons on the top right side of the journal fields that help you toggle. This button gets hidden sometimes for a specific user which makes the user not able to toggle between showing one or multiple fields.
- The reason behind this behavior is because under Activities filter (the funnel icon on the right of the Activity Stream), one of the journal fields is filtered out. (Screenshot below)
- This is in fact, an expected behavior because it doesn't make sense to have that "unchecked" journal field TO BE on the form (Form Layout) as any data posted in that field won't be stored in the Activity Stream.
- This is by design and hence, in order to bring back the button, check back that field in the Activity filter.
The Activity Stream filter is handled via specific user preference called "incident.activity.filter"