Notifying a single user in a declarative pipeline

Is it possible to retrieve the slack userid from the jenkins user who started the build in a declarative pipe ?
Using @slack-user-id implies you already have the slack user id, what if we want to use the one saved in the jenkins user profile

No file, test, or entry point is named. Start by reviewing the issue discussion and tracing how declarative pipeline notifications access the build-starting Jenkins user and profile data; done means the initiating user's saved Slack identity can be used for a single-user notification.

Written by the indexing model from the issue text.