I finally got around to reinstalling TS3 on my new computer. Well, it sees my Library and Saves folders. It does not see my Mods or DCBackup folders. I should mention that I keep a backup of the whole Sims 3 folder which include the Mods and DCBackup folders on an external drive for easy restores. I've tried deleting cache and checking to see if it's looking in the right place. The strange part is that it sees NRaas mods, but nothing else. I can't select my custom worlds or lots. I can't select my saves. I renaming my sims 3 folder to Sims 3Backup and letting the game regenerate a new Sims 3 Folde and then putting my old mods and DCBackup folder in it. Nothing. The launcher does see lots as uninstalled, but it only sees lots, not everything.

Tried restoring everything from a backup. Still nothing. I moved my .sims3packs into Downloads, but only Lots show up in the launcher and they're already listed as installed.

I think you might be confusing DCBackup with DCCache for a start. Content that is Launcher installed lives in bundles in DCCache, the game reads the content from here upon startup. The dbc bundles are CC, the ebc bundles are store content. Does your current DCCache actually have any content bundles in it?

The only purpose of the files in DCBackup is to allow already installed content to "stick to" sims and lots when they are exported out of the game for others to use. Other than that, it can remain empty except for the one required ccmerged file that must stay in there to allow premium store content to work.

Your custom lots might not be usable if the content they rely upon is not actually installed on the current game folder, one way or another. Saves that depend on custom worlds being present will not be selectable if the world is not installed and it must have an entry in the InstalledWorlds folder.

Unfortunately, my problem was more related to my entire documents folder of TS3 being corrupt. I had to dig out a backup of my downloads, mods, library, everything from an earlier point in time. I should have noticed that everything was smaller than before...