I start with:
CREATE VIRTUAL PROCEDURE
BEGIN
SELECT * FROM PartsSource.PARTS;
END

At this point the Criteria Builder (and Expression Builder) button is disabled. So I click in the SELECT clause to enable the button. Let's say I click between the P and the A of .PARTS. The button enables, I craft my WHERE clause, click OK and wind up with:

CREATE VIRTUAL PROCEDURE
BEGIN
SELECT * FROM PartsSource.PA WHERE PartsSource.PARTS.PART_COLOR = PartsView.getPartsByColor.colorInRTS;
END

Regardless of where in the SELECT I click, the WHERE clause should be inserted in a syntactically correct location.