Where are offloaded apps stored?

Short answer: In the Storage Studio folder on your fast drive. The Offloaded tab lists each archive, when it was made and the total space used.

In the Storage Studio folder on your fast drive. The Offloaded tab lists every archived app with when it was offloaded and how many items it holds, and shows the total space they use on the drive.

Manage them only from that tab — Restore or Remove — rather than editing the folder by hand.