"Use a midpoint for any unknown portion. For instance, if only the year is known, use a date in the middle of the year, and if the datetime is known down to a day, use noon for the time."

Group them how / where? I'm reading this as "to present the volumes together in a IIIF viewer" or similar, with an implication later in the sentence of changing "while maintaining . . . " to something like "while allowing the user to browse each volume separately [as well]".

Serial comma, so "label, or description"

Should be https

Add to implentation notes above: "If the exact time is not known, then “00:00:00” should be used. Similarly, the month or day should be 01 if not known."

And change here to 00:00:00

"lack of viewer support for date-aware navigation for single manifests"

consumption only by

Put bit about defaulting to zeroes here.

change to "resources"

I'm inclined to say "a creator field" rather than assert that the field itself is defined by the English label value.

"descriptive metadata field labels"?

dele

"with the Manifest"?

Need to use the baseURL Jekyll property?

values (or whatever way stays consistent with labels previously.

requiredStatement

"no assigned language"?

"image of the painting commonly known as . . ."

label