Hi @iderryan
As it stands, we currently do not have a library for sketch symbols. For now, your best bet is to create a drawing with all the sketch entities that you require. You can then Copy/Paste the sketches between drawings.
This is a feature that is on our public roadmap, and I am actively tracking requests for it. Every customer request that we get, from meetings, emails, forum posts etc. gets collected and categorised in our feature request database. This information is used to prioritise the features that we build next. I've added your request to our database.
The Fusion drawings public roadmap is available here

I'd love to hear from you directly, and to get your thoughts around sketch libraries. If you're up for it, here is a link to my calendar, please book a 30-minute session with me, and we can chat on Zoom. I can also show you some of the new tools that are coming soon