Is the Plaintiff allowed to enter motions for a judge’s consideration in small claim in Washington?
No, usually in a small claims court case, you get one shot at making your case, which is in court when you actually appear in person in front of the judge presiding over the matter. You can maybe compose a written memo outlining your evidence and the legal points of your case and possibly submit it to the judge ahead of time, but you will need to make sure that the other side gets a copy of what you have submitted well ahead of the court date.