Hi mate,
Thank you so much for the kind words!
It is extremely motivating to hear your positive initial impressions about our work.
To the question:
You won't be able to assign shortcuts to SGC thumbnails, but you can use Next/Previous Frame In Symbol commands with shortcuts to quickly go through the content of a Graphic Symbol.
Hopefully, this will give you the desired quick access.
In v.7 there will be improvements to SGC and even more ways of choosing 'first frame'.
You've probably already had a look at our rigging and posing system, SMR. There will be a bit of a learning curve there, but everything is logical, and it's been around for a while now, so the UX is quite polished.
We hope that you will enjoy using it!
Thanks again for stopping by and sharing your excitement with us!
Good luck with your projects!