Capturing an 'Assist'
If you want to capture the details of a property which you never held an interest in, but were active in protecting, use the 'Partner Holding' status field:
You can name the partner in 'Active Contacts' and capture other details of the transaction using the rest of the property record.
Capturing a Property Transfer or Disposition
If you transfer your interest in a property to another organization through sale or any other means, use the 'disposed' property status. Note that this is different from 'Partner Holding' in that you did actually own this property or property interest at one time, as opposed to simply assisting in its protection.
Changing the property to 'Disposed' will add a 'disposed on' field to the list of available fields in Property Details. If you want to capture more information on the disposition, you can add a Disposition Asset, which has its own set of details pertaining to the disposition, including who the grantee was, how much the agreement was for, what type of disposition it was, etc.:
Depending on what your management responsibilities are after the disposition, you may need to also update the stewardship site status to 'inactive'.
Notice that in both examples the interest field stays the same -- 'Easement' - there is no need to change it!