While you are not able to merge your accounts, you can find your designs and use the redesign feature to copy and paste the link of your design(must be in public status) to your new account and save them.
I ended up buying another seat for $299, and guess what happened. It simply converted my account to the new seat, and still shows only one seat. It never added another seat. So now I have paid $871 (1 seat for 12 months + 1 seat for 6 months). My card was charged. I have the receipts and the Homestyler account only shows 1 seat of 6 months. So what happened to the 12 month seat? This is fraud.
