Omnibuses of novels abound, some edited and formatted wonderfully - like HarryT's ER Burroughs

- and some not. Love to read them, if the formatting's not distracting, but how do I catalog them? They're a higher level of abstraction than "book."
In my former placid pBook universe, I solved this dilemna mostly by not buying omnibii unless a novel was available only there. So it was a rare case in my printed out pBook spreadsheet that I took along to pBook stores so I wouldn't buy books I'd already read (and still owned because I might read it again someday), or already read and trashed (because I wouldn't read it again.) And I solved the occasional exceptionn case there by listing novels subsumed in Omnibus books as separate records, with a symbolic indicator meaning 'a subsumed novel in an omnibus listed elsewhere.' And listing trashed books at that same level of 'not an actual book.' Similar to calibre's empty book concept.
But in this not so placid eBook universe, what should I do?
Say I want a search to find Tarzan and the Jewels of Opar but I don't have it listed that way under the title Tarzan Omnibus 1 (HarryT's). If I didn't think to list all the subsumed novels in parens in the title field, making an unwieldy long title string, I wouldn't find it. Novel names as tags?-yuch. Custom column just to handle this? - doesn't solve the search problem.
How do other people, especially professional librarians, like to handle this problem of different levels of abstaction in their cataloging? I'm leaning toward the same method as in my pBook spreadsheet, separate novel records with symbolic indicator of 'subsumed novel in Omnibuses elsewhere' and perhaps the Omnibus title in a comments field.