Hey.
Yeah, so new format using array: true is meant to be implemented for all attribute types, but for now it really is only available for assets, even strings - is not really an array, but a set, where you can’t change order nor can have duplicates.
Plan is to add support for multiple values for other types indeed, it is in backlog, can’t really give an ETA.
Regarding entities case, you could look into tagging - that could work in some cases.