Currently, it appears that the process flow view (for either Portfolio or Feature Epics) of a Jira Align backlog does not allow for any DONE items to be hidden from the view at any point in time.
In JIRA, we can configure the board to drop DONE items after a certain number of days/weeks etc or after they are officially "released" with a fix version. Is this functionality allowed in Align? The DONE column is getting quite long and cluttery after a few years.