Asset dynamic subfolder for User Matrix I need to set an asset field's dynamic subfolder path to the User ID.

The field is within a matrix.

The matrix a field in a User profile.

Setting it to {currentUser.id}, {owner.author.id}, {object.author.id} results in an invalid path message when trying to upload to the asset field.
You should be using {{currentUser.id}} instead of {currentUser.id}

The difference is that double curly brace syntax works on the global scope, while single curly brace syntax tries to resolve itself on the current element. Relevant documentation.