The scanner correctly identifies the name of the first album as “Havoc and Bright Lights (Special Edition)” with a “Disc 1” designation. But the second one is identified as “Havoc and Bright Lights” without the “(Special Edition)” part of the name (although it does show it as Disc 2).
On another example I manually edited the album name in Plex so each disc name was the same and the library then displayed the album correctly, but I don’t think this should be necessary.
As I said, I have a bunch of other examples of 2-, 3- and 4-disc sets, where one (and I think just one) of the discs is incorrectly identified (but not always the last disc in the set).
I use a slightly different folder structure for multi-disc albums that (in combination with ID3v2 tags) seems to work well with Plex and other media systems that I use (Emby and Roon).
So there is a single folder (Album Title), with individual folders under it for the contents of each CD.
In each of these CD folders, I use a metadata editor to ensure that all tracks in all CD folders use exactly the same album title, and that every track, in addition to a track number, is assigned the relevant disc number. Thus in folder CD1, all tracks are assigned to disc 1, in CD2, all tracks are assigned to disc 2, and so on.
Edit: and, as OttoKerner has reminded me, all tracks must have the same Album Artist assigned to them…
I verified the metadata is correct for all tracks on both discs. I tried the naming method suggested by @gcoupe above and it is working properly. I used to have this naming scheme a long time ago but I think I was having problems with iTunes. In any case, it’s working for both Plex and iTunes now, so thanks to both of you for your help!