Python-based custom agents belong to the group of “legacy” agents.
In preparation of their eventual removal, they are now no longer shown by default.
There is a new checkbox in Settings - [server] - Library to re-enable them for the time being.
(you might need to update the server to 1.43.x for this to actually show up. use the hosted web app.)
Instructions about future custom agents are slated to be published shortly(ish).
