Yes, it's possible on Steam, but not perfectly straightforward. Soundtracks are usually listed as separate DLC or apps, so you can find them by filtering your library manually or using dynamic collections (e.g. filter by type: "Soundtrack"). However, Steam doesn't offer a built-in "OST" filter, and tagging can be inconsistent. For better control, you can use tools like Steam Library Filters or create custom categories to manage your soundtracks more effectively.

Not talking about finding the OST i bought
Asking about Shop's search, I see no option like "only show for my games" or something like that
example I'm searching for "OST" and the thing is I see no filtering like only show for my games
In short, I see no option to find / show only OST for games in my library.