Yes, certainly! Go to Events > Your Events > Jobs, and click the name of the job you would like to turn offline (or back online). There is a checkbox at the top of this expanded job to make the job offline/online.
If you’d like to turn a shift (or set of shifts) offline, go to Events > Your Events > Shifts. Click the job on the left, and then click “Review Shifts” in the top right-hand corner. Expand the shift you’d like to turn offline, and use the checkbox inside the shift detail to toggle the shift on/off.
When you turn any job or shift offline, even if there are volunteers registered, no data will be lost or removed. Those offline jobs and shifts will simply be removed or hidden from your sign-up page so that no new volunteers can register for those positions.