What technologies do you think exist but are kept away from public disclosure?

probably lots of backdoors and decryption tech, but not much else.

also probably growing artificial human organs and/or research on human gene editing

Space tech.

because imo the major event of the 22th century is probably gonna be space travel/warfare/colonialization

and any nation would be dumb to not keep their space stuff well-hidden lest someone steals/copies it

• More modern nukes. Considering the most modern nuke (b83) was invented at late 1970s, and officially put in service at 1983. It's very likely a new nuke was invented in secret.
• Bio weapons more lethal than botulism
• Cyber attack bots
• Other warfare related stuff