Can I still view all of my chat transcripts, history, or notes once the event has closed?

Yes, this is located on the My Journey tab on your event card under events.

Yes, this located on the "My Journey" tab under the name of the event. The "My Journey" button is located in Events > under the name of the event card.

This will show you the data of what you did during the event. Each event you attend will have its own "My Journey". It will show the organizations you looked at, notes you put in and all of your chat messages.