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Hi John,
Thanks for posting in the community. We are happy to help you.
A SharePoint list can have up to 30 million items, however, there is a known limitation for the list view threshold, which is 5000 items. I'm afraid that there is no way to change this limitation.
Regarding your questions, List above 5000 items is indeed possible with planning and some filtering/sorting compromises. Sorting such a list directly may cause problems or list view threshold errors. In this case, you can add Indexed columns to the list and set filters in the list view (click "Modify list view" and set filters to limit the number of items in the view to less than 5000). After that, you can sort items and place them in folders.
For your reference:
Living Large with Large Lists and Large Libraries
Create, change, or delete a view of a list or library
Manage large lists and libraries
Sorry for the inconvenience that happened to you. Appreciate your understanding and patience.
Sincerely,
George | Microsoft Community Moderator