Proposal: UI Hints in USD

Hi all,

I’ve just posted a PR proposal for expanding presentation metadata (aka UI hints) support in USD. Things like specifying a particular widget type for use when displaying an attribute, min/max values that numeric fields can enforce, and expressions defining dynamic hiddenness for attributes and display groups.

PR here
Rendered view here

Feedback welcome in this thread, or on the PR directly.

Thanks!
Allison