Reviewing old posts it seems that there was once an easy weld annotation object as part of the AC 9 library (in a sub library called NCS detailer) which had simple pull-down style choices for the weld elements (like the sizes in the wood member detailer or the shape and size in the steel sections) and though we are mostly not structural engineers using Archicad (except of course Riverstone Structural Concepts and others of their progressive and brilliant ilk) - we all do often have to detail welds for sunshades and railings and so on.
It would be wonderful to have a modern version of this old library part brought back into play!
This one might help you out. It has some quirks that I have been too busy to deal with but if you can get around them (mostly to do with scaling) then it should work fine. Just place both the .gsm and the images in a loaded library.
AC 19 6006 & AC 20
Mac OS 10.11.5
15" Retina MacBook Pro 2.6
27" iMac Retina 5K