I'm pretty sure this isn't possible, but I'm going to ask the hive mind. Looking to implement a standards based secure virtual machine credential to use from web based applications that can be automated. I know, a lot to ask
One possibility is Windows Hello - however automating that is hard as it is not allowed to be used whilst connecting to a machine with RDP - this is used by most RPA solution providers for creating sessions. If you can get it working, then it can be authenticated as a platform authenticator.
Passkeys can be created on a different device to the consuming application. However, as I understand it, the user presence check (e.g. BLE or OOB check) is required to ensure that either the user is present, or that the user has approved use of the portable key.
Is there any possible scenario where a passkey credential (or other webauthn credential) can be used by the web credential APIs without user interaction on a separate device (other than a platform authenticator such as Windows Hello)