If you are looking to create an audit trail, there is the Audit Trail module in the App Store that may be of use.
If you are just creating a note entity, then you could check the Store ‘owner’ option in the domain model. When it’s created it should store who created the entity automatically, and you could just retrieve this as needed.
To add on to Roberts answer, if you set up your entity to capture Owner and ChangedBy, as shown below, Mendix will store the Owner (the user who created the object) and the user who last changed a given object. Note that Owner will never change, but ChangedBy only contains the user who change the object last.