In Heptabase, all deleted cards and whiteboards are moved to the trash can.
To find the trash can, click on the Heptabase logo at the top-left corner of your desktop/web app. Alternatively, you can type Cmd/Ctrl + K to trigger the command palette and search for "Trash" to access it.
Inside the trash can, you will find all your deleted cards and whiteboards. Click on them to either restore or permanently delete them.
If you want to permanently delete all items at once, simply click the "Empty trash" button.
If you permanently delete any cards or whiteboards, you will NOT be able to restore them from their version history.