It's possible to lock a period in the schedule view in Quinyx.
Go to Schedule in the top navigation bar, click on the three dots and then Lock schedule.
Select a to date where all schedule data (shifts, punches, absences) will be locked backwards in time. You can't make any changes in a locked period, except to attest, unattest punches and absences and adding/editing of manual salary types.
A locked schedule is visualized with a white/pink border between the schedule and the toolbar. You can see the date to which the schedule is locked on the left hand side:
You can't add/edit/delete a manual salary type in a locked schedule period: