Btw, the doc https://plugins.jetbrains.com/docs/intellij/plugin-signing.html says

A plugin author generates a key pair and uploads the public part to JetBrains Marketplace (this feature is not yet available).

It is kind of supported. In JB user profile, there is an ability to upload a public part of an SSH key, which can be also stored on YubiKey (with private key). You just need another field like that, but for signature verification, because different keys might be used for signing & auth, see https://stackoverflow.com/questions/73673920/do-i-need-authentication-as-well-as-signing-keys-on-github#:~:text=The%20difference%20between%20signing%20keys,may%20be%20added%20for%20both.