I think I understand your question and had an answer (long time ago) that might be what you ask. At the time the question related to creating a wedding album with separate collections of events at the wedding sorted.
1) Sort each Collection of the series in the Custom order you want for each.
2) Create a new "Empty" Collection (without any images) also set the "empty" collection to the TARGET COLLECTION
3) Immediately set this empty Collection to "Custom Sort" (sounds silly, but regardless of there are no images, and you must click on the Sort order option menu. )
4) Now select all images [Command+A Ctrl+A] in Collection '1' and drag and drop all into the "Empty" Collection. Make sure you drag using the FIRST photo in the Collection.
Or- Instead of Drag&Drop, you can select the FIRST photo in each collection, do [Command+A Ctrl+A] to select them all and hit [B] to place them in the "empty" collection.
5) Repeat step 4) for each remaining Collections 2, 3, 4, etc, in turn by number order.
The result is that the "Empty" collection will now have all your images sorted as you want-
Collection "1" sorted, Collection "2" sorted, Collection "3" sorted, Collection "4" sorted, etc.
(Do not try to reset the Sort option)
6) If you want derivative images with a sequence maintaining the sort: Export the "Empty" Collection using your Sequence Rename Preset- (eg. "Sequence_Filename").
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