If the Title is using the 2D Script to generate the title, then you can use the Pen command to set the pen for each element. Is this an ArchiCAD Title, or one you created? The assigned pen number will have a line weight based on the setting in the Pens and Colors table.
You should add a Signature to your Profile (click the Profile button near the top of this page) with your ArchiCAD version and operating system (see mine for an example) for more accurate help in this forum.
Still looking through the editor, but so far I've only found, with the editor and script, only the ability to edit the line-weight of both the circle and the line together, not separate. Either I'm just missing where it's at in front of me or I need to learn GDL editing better (probably both).