Hi Zachary,
Please refer the screenshot attached below, I believe this is what you are referring to, is that correct?
By default transaction Library is selected, but once you click the folder icon(highlighted below) it shows all the 'Transaction' Libraries.

There's no way to set library as favorite as we can set the teamspace/Applications as favorite or default. you can raise this is an idea on idea portal for future releases.
Regards
------------------------------
Hammad Naeem
Precisely Software Inc.
------------------------------