Hi @Rflong7! I just wanted to bump this thread to make sure the wave of Simmers now able to use EIG see it AND to thank you for figuring this all out on your own and sharing it.
I had this problem a long time ago, when my addiction to the Sims 3 Store began. You were such a huge help then, but it took me forever to set aside the time to reinstall just the build/buy items I needed—I wasn't able to open EIG at all, since I owned just about the whole Store. I finally cut my DCCache down to 2.19 GB (an exhausting feat!) and was thrilled to finally have EIG load. But, the excitement was short-lived when I found out that I could load EIG with that much Store content, but not save in a built-up world. I had two options: try to install even less content next time OR give your method a try. I don't mind poking around in my game files, but this was a bit scary—but your tutorial made it so easy! It took me all of five minutes to sit down with my saves and a back-up, and go through your steps.
I've only added two lots (so far), but I take that as a huge victory! This is the first time I've ever successfully used EIG, and it's all thanks to you. Thank you, thank you, thank you!
So, for the Simmers out there having trouble with EIG even after the new patch, I highly recommend looking at the amount of Store content you have installed and following Rflong's tutorial—it is surprisingly easy to do! I didn't even rename any layers or lots—I just made a note of what I had already called things and that was it. Took me maybe 10 seconds to save in EIG!
