Not yet. There is no way how to define default weight for all non-peer assessments. However, I am planning to implement another allocation plugin that could be used for this. That allocation plugin will appear as a third card next to Manual allocation and Random allocation and will be probably called Self allocation. It will allow the current user (that is usually a course teacher) to allocate all submissions to themselves in one click. And they could specify a weight for such assessments.

That allocator would be useful for teachers who assess all submissions as a parallel to the peer assessments. So then you will be able to allocate all submissions to yourself with a weight say 4 in one click (instead of going thru the list of all submissions and clicking Assess this submission to create the allocation).