There seems to be an explicit restriction in the UCI that doesn't allow the creation of a blank record.

If you run this code in the classic interface:

const data = {};
Xrm.WebApi.createRecord(targetType, data).then(...);

The appropriate record will be created as expected.

However, the same code running in the UCI generates this error:

"UciError: Required parameter is null or undefined: data"

Please remove this restriction.