After some work, I was able to separate the RE List functions from the actual Element data. So, the list no longer needs to sort through all the RE Data to display the list of elements.
This has resulted in a DRAMATIC speed increase with large, complex scene files.
Before, people would notice huge slowdowns and beachballing when the RE Dialog window was open. Every time the dialog would need to refresh, it would cause a beachball. Now, it refreshes very fast, and I feel confident the dialog can be docked without significantly altering the user experience. Because if this, recording and loading of Render Elements will be much faster, as well.