Is there a way to create multiple global swatches with an existing swatch group? I have shift+clicked the swatches in the group and went to the group folder but the convert process to global tickbox is greyed out.
It's not possible to do this from a floating, independent, library panel.
You must add the swatches to the main Swatches Panel first. You can do that by simply clicking the Color Group Folder icon in the unique library panel.
Then in the main Swatches Panel highlight only the color swatches not the color group folder. And from the menu choose Swatch Options. (Note, if you have the folder also selected the menu will read "Color Group Options" and is not what you want.)
Don't highlight the little folder. Only highlight the swatches. You will then be able to set the swatches a global.
Most external swatch library files are in .ase format and can't be opened directly by AI - they can merely be loaded as a panel. The .ase format means they can also be loaded into Photoshop or InDesign as swatches!
But, if an external swatch library happens to be in .ai format, you can open that library file directly in Illustrator and then convert the swatches there to Global.
Save and close the file.
Then, in the future when you load the library, the swatches will be set as global in the floating panel.
To be honest, I don't really know why all the swatches that come with AI aren't already set as global. I mean, it makes life so much easier ultimately. I can only assume there's some sort of compatibility issue with the .ase format.