Stacking doesn't have the same purpose in MC—it's primarily for maintaining different file versions of the same media. There is a Play Stack command that could be used to play stacked files/discs, but it's only available in Standard View. The only practical solution I've found is to mux multiple-file videos together into one MKV file.
Stacking is not a good solution for grouping related items. To group by movie series or franchise, use the same method as for anything else (i.e., Genre, Year, Director, Rating, etc.). Tag the files with the value you want to categorize by—in this case, using [Series] or a custom [Movie Series] or [Franchise]. Then include that field in your view as a Category.
If you expect this to work exactly like XBMC, you're SOL. But in addition to being much more flexible, the MC way is not so bad for things like this. In Theatre view you have the choice of using one view or two for movies. Using one view with a [Movie Series] category, you would first see a category list of all movie series. To view other movies, you would select 'All Movie Series' to view a list of all movies—whether a member of a series or not. Or you could use the expression-type Category If(IsEmpty([Movie Series]), [Name], [Movie Series])—to include other movies in their own series of one so they appear in the category list. I prefer to use two views. My primary view does not attempt to group by [Movie Series]. In most cases, the movies are named so series appear together anyway. I use a supplementary view that includes only movie series, and is grouped by [Movie Series].
You're free to ask—as some others have—for some special treatment for movie series in Theatre View. But Theatre View already has a simple and effective mechanism for grouping—Categories. Grouping by series and the need to do so are no different than for other Categories. It's up to the user to decide how to configure views in way that serves their needs and preferences best. I find that usually comes down to finding a comfortable balance between the number of categories used in a view versus the alternative of adding additional views. Adding category which won't often be used or doesn't logically fit with other categories used isn't a good choice when a more logical, dedicated view can be only a few button presses away.
I do see some merit in an addition mechanism for grouping files—one which expand/collapses groups of files in place in the file list—much like stacking does. That would offer more choice in how things are done, but it's not required because grouping is otherwise impossible. And there are already many such things in MC that most users aren't even aware of, or don't use because the number of such options makes the whole thing to difficult to figure out. In any case, even those who can't agree on how important this is probably will agree it won't even be considered until the next time there's a major overhaul of Theatre View.
