As per the title.
We need client scripts to apply at a Quick Create level. We enforce logic on the form to ensure data quality, automate field values, etc. However, all this is lost when a user attempts a "Quick Create".
It is disappointing because, from a workflow customer experience perspective, Quick Create is the preferred method as it allows the user to stay on the original record.
Please support this ASAP :)

Moderation Update:
The capability extending the Client Script functionality to customize Quick Create forms is now being rolled out in phases, To know more refer to the announcement post.