I'm want to use the same textures for REX4TD and Soft Clouds in my P3D setup as my FSX setup, but I never made a theme. I kinda just uploaded them one by one. So, yeah, where can I find what textures I am using. 

I made a post on the Rex support forums months back to answer this question and their answer short and simple was, there is no way without a theme besides manually installing and comparing.

Well, I'm pretty sure the backup folder has it all... sigh. It was SOO much easier with essentials. Thanks.

I love what REX4 brings to FSX with DX10 preview, but I think their current interface's functionality is half finished in its implementation.  To force feed the notion of "you have to create and manage themes" really stinks IMO.  They should at least mark the most recently loaded set as such when you walk through the interface's set selections.  I'd love to hear why they can't do this.  As a professional software engineer, my take is that they simply don't want to pay to develop such simple enhancements.  BTW, when REX4 first released I did post this short coming on their site and their response was "there will be future upgrades" with no specifics given.