You can archive a field when collecting it's data is no longer necessary. Archiving a field hides it from the process, however, its retains the data that has already been entered and can still be chosen as a column in a View. Old forms will still show existing data from archived fields, but adding new data will no longer be allowed. Archiving is recommend over deleting a field in most cases to preserve references to other processes and older form data.
Top menu >> Setup >> Click process >> Fields tab
To archive a field, hover on the field and choose Archive.
The field will now be removed from the template and placed in the Archived fields list.
If you ever need to start tracking data for this field again, you can Activate the field from the Archived fields list.
The field will be returned to the Fields template at the bottom of the page. You can move the activated field into the desired location by dragging and dropping the field.