the quinary note and the quinary augmentation dot
so basically the quinary note value is one of any note value tied to the aforementioned one.
so that would mean that the augmentation dot would be like adding a value that is a quarter of the note that this dot appears after to the note
he probably explains it better: https://www.youtube.com/watch?v=2AHilNBAHwg
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There is no standard settled on quinary notes (a few months ago, someone posted about the use of a star instead of an augmentation dot).
If you'd like this symbol to become part of the notation standard, then best to take it up to SMuFL (https://www.smufl.org/). That is also the standard MuseScore follows for functional musical symbols.