Document merge in CiviCase from scheduled activity in timeline
The print/merge activity type is usually a &quot;system&quot; type that gets created when you use the print/merge search results action, or the Export Document button on Manage Case, not an activity you usually create yourself. The fact that it works from the add activity dropdown seems to be because of some sneaky code that was added to make it do the same as the export document button: https://github.com/civicrm/civicrm-core/blob/915e9edd65c7b594372897923734ec52e67f1835/CRM/Case/Form/CaseView.php#L248-L251