You’re new to Weldments in SolidWorks and excited to start using structural members, only to find that the default weldment profiles are limited to a sample of the ISO standard. Then you ask, where are all the weldment profiles?
Presumably to save space, SolidWorks made all of the weldment standards downloadable from the design library folder, in the task pane. The video below will show you the procedure of adding in those extra standards, and then you’ll be on your merry way.