Create an API key

The full key is shown once, with Copy beside it. Refreshing the page does not show it again.

Who can do this. An owner or admin on a paid plan, under Settings, then Integrations, then API.

Open Settings, then Integrations, then API.
Under API keys, enter Name and choose Access: Read, or Read and write.
Press Create key.
The card is titled Copy this key. Press Copy. It changes to Copied. If the clipboard is blocked, the key field is selected so you can copy it yourself.
Press Done, I've saved it. The card closes. The full key is not shown again after you leave or refresh.
A stored key shows its prefix only. Press Revoke to stop it. Keys are stored as a hash.

Can I open the API settings again and read the full key?

No. The key is shown on the card that appears immediately after Create key. After that, the list shows the prefix only.

More on this part of Shiftbrook: API docs.