Sure it works:
Without loosing your TM Backup:
- Add a partition (disk7s3) on the 512 GB SSD with the size 256 GB (by splitting disk7s2)
- Clone disk0s2 to disk7s3 (or restore TM to disk7s3) and restart from disk7s3
- Clone disk7s2 to disk0s2 and erase disk7s2
- Clone disk7s3 to disk7s2 and restart from disk7s2
- Delete disk7s3 and expand disk7s2 to the full size
- Just reinstall your current system on disk7s2 to create a Recovery HD if none is existing without loosing any (personal) data.
- Swap the drives
Loosing your TM Backup (not recommended):
- Erase disk7s2
- Clone disk0s2 to disk7s2 and restart from disk7s2
- Just reinstall your current system on disk7s2 to create a Recovery HD if none is existing without loosing any (personal data.
- Swap the drives