Games that can be added/removed manually from library:
- DLCs
- Pending games (i.e. games that aren't dropping cards yet and not showing up in your public library yet.)
- Steam packages (because they don't show up in public libraries, but they're discovered by the user API, just like both above.)
I don't think Barter does the distinction for pending games. Maybe you can add them through one of the JavaScript extensions, though.
Games that you mentioned are:
- One is an episode (you can buy episodes on Steam but you can't get a Steam key for them, so they're not tradable... And usually, you buy the whole series so that's the thing that's potentially tradable.)
- Config titles, i.e. internal stuff that isn't tradable. One is a Mac version of GTA, which is included in the game when you install it, it's got its own app ID so it's listed at Lestrade's, but if you want to get that, you need to install the parent game. (Or sometimes sibling game, depending how I set up the relationship in the database.)
Generally, anything that gets its own app ID but is installed as part of something else or not found on the Steam store (retail-only keys, level editors for a parent game, private server software, demo, trailer...) won't be tradable on Lestrade's. And thus, can't be removed from your library manually either. I'm flexible on changing details, though! But generally speaking, LT's/BVG's database is really full of stuff that shouldn't even be in there... Which is why they're not discoverable by default.. (You have to select 'junk' in the search type.)
For instance, whenever Steam does a publisher sale weekend, it creates a store page which internally has an app ID, and you can access it through that app ID. This ends up in their huge database and the Steam API returns the type as 'advertising', but... not always. (App types are done manually at Steam, sometimes I guess there are human errors. Which I then manually fix on Lestrade's. But then again there's also human error at Lestrade's, ah ah.)
BTW I suppose you've tried adding games via the 'Add DLCs' button, too..? Sometimes it helps where other solutions don't.