As a stakeholder, you can convert an activity to a process. You may have created an activity and then realise that it should have been a process as there is too much detail in that one activity.
You must be an administrator or have the create process permission.
Quick Steps to Convert an Activity to a Process
From the diagram content menu, select the actions icon --> Convert to Process, or
From the activity actions menu, select Convert to Process
What happens when an activity is converted to a process
The process name is the same as the activity that was converted
The process owner and process group are the same as the original process
The process author is the person who performs the conversion
All the activity tasks are converted to activities within the new process
Any attachments and notes become process level attachments and can be found above the process start on the process steps in the right-hand diagram content menu
The new process is automatically linked as a process link where the original activity was
To undo the conversion, you could convert the process link on your map to a task and then convert the task to an activity. But the actual process that has been created doesn't disappear, it would need to be deleted.