(If this violates the "Other Sites/The Exchange/BBS" rule, I apologize. It doesn't feel like it should, but it could technically fall under it, so I'm apologizing in advance. The existence of pages like this made me this it follows the rules.

Often, once I've purchased a set from The Sims 3 Store,it's not where I would expect in-game, such as the Feathered Table Sculpture being under Decor; Miscellaneous instead of Decor; Plants. It drives me nuts and can take up to 30 minutes to find, if not driving me to give up the search all together. Does anyone know if there's a list out there of where to locate these things? And if not, would creating such a list be a project be worth undertaking? Are there enough other people who buy DLC and have this problem that if I were to do so, would it be used?
Thank you.

I don't think such a list exists, there are simply too many objects - literally hundreds - to categorize. It would be a huge effort. You are right that sometimes content is assigned to categories it wouldn't make sense to be in. The Misc Decor section is a nightmare to load and navigate.

BUT the good news is that you can organize stuff yourself! This tutorial applies to content delivered through the basegame, EPs and SPs, but with a little work before it you can follow it to the letter. For content that is "outside" the game - Store content, custom content - you don't need to clone anything.

1. Run (drag-and-drop) your .sims3packs through S3RC (the executable within the "s3rc-win.rar" file).
This preserves the object name and description within the catalog.

2. Convert the .sims3packs to .packages with the Multi Extracter.

3. Open the resulting .packages with S3PE and make all the changes your need: for objects (OBJD entry), for CAS content i.e. hair and clothes (CASP entry)

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For patterns it's slightly more complicated: extracting them outright with the Multi Extracter can lead to something that, in turn, leads to the Materializing Materials error (basically, CAS is stuck loading and this message is displayed on screen).

1. Why this happens
2. How to fix it
3. How to change the categories of patterns with another program called Postal

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It can seem overwhelming at first, but it has numerous advantages, especially if you stick to .packages as much as possible. After a while it'll be second nature to do stuff like this, and to me it's a huge advantage to be able to install and uninstall content very easily, as well as decide where in the catalog I want stuff to show

If you have any questions, ask away!

Agree with Sweetdevil (huge amount of Sims 3 items) and thanks for link at "Sims_3_Catalog_Reorganization".
Hi, Pixie_child!
This was a reason, why I've fighted with undeletable featured sets collections - I'm making for store items my own collections (in clean game-folder), because I've had too still difficulty to find EPs/SPs/Store content. Mine collections are bigger for not having them many in that not expandable window in game and I'm putting there more sets together. You can add for yours collections custom image with Inge's Collection Tweaker 3. Second my opinion, this is still less work than recategorize all store content - but obviously this is up to you, how you want it have in yours game.
As I'm obsessed with CAStability and V-Shifting, I haven't still moved on recategorizing (I believe, that EA clothing/hair has too many things to fix and amount of files is still huge) except store clockwall shown under fences category, some unhidders and female wrong-categorized flippers due to huge amount of store files (for 20 ebc files I have in my DCBackup folder 4.140 packages and I haven't still installed individual clothing and hair - obviously, not all packages from those are requiring recat).
(Sorry for my english, but it isn't my native language).
Happy 3-Simming!

I remember that crinrict made something for Store items, but can't remember exactly what.
There also used to be Mr Hawk's Simalogue site but it seems to be in hibernation (I think he lost his data).
None of these, however, provide exhausting information for what you want to know.

You are intending this tool? http://sims3.crinrict.com/en/s3s-browser (Sorry for MrHawk site and I'm missing him too on EA site, it was very nice person :'( )
(I have too some self-made store (organized by store categories) excel lists - those are including direct download link, Sims3Pack name, EN Store name, what is including each set, with links at store pages and EA thumbnails. Those are still WIP and not deserving to be uploaded, because still finding errors and aren't including category in which can be item found in game).