I was recently asked to create an annotated line tool by a user on this forum.
I personally believe that this sort of thing should be handled by Graphisoft as part of the built in polyline tool. However, as it was a simple project and the need was there, I decided to help out.
The end result is a polyline GDL object that has flexible arrow and annotation components.
The intended use is to represent service lines coming into the site for services such as water, waste, and electrical. Hence I have actually used the MEP GDL subtype with the intention that this 2D polyline could include 3D MEP components in the future.
Let me know what you think and if you would like to see it become a legitimate 3D MEP tool.
Creator of Cadswift's parametric GDL libraries
Creator of Infinite Openings and Component Catalogues
Push the envelope & watch it bend