Drupal 8 Rules – Update or definition of a custom field by the user when creating a new node of a specific type

title just tell everything 🙂
I need to a ruler this defines a value users custom field (ex. field_custom) WHEN a new node type (ex. page) is created / saved.

For me, it seems that I can only access the fields of this node that triggers this rule event. But I want to edit a profile field of the current user …
In the dropdown list of data, I see "node", but also tokens starting with @. for example @ user.current_user_context: current_user.
But I do not know if I can use them. Try to set the value via @ user.current_user_context: current_user.field_custom seems not to work.