Spatial referencing is one of the fundamentals in ASL production that I cannot imagine writing without the ability of establishing referents in their specific space as we do in ASL.
There are existing symbols for pronouns, but something is missing for determiners. So, I came up with a spatial reference system in December 2014 as demonstrated below. It is a modular system that is easily added on a writing system without changing the original writing system of digits.
The illustration of ASL writing below shows a paragraph based on the ASL production in the video above. You will see the ASL speaker signing with determiners, pronouns, possessives, and a reflective pronoun in this one paragraph. She translated that into ASL writing which shows below.
The symbol X represents an indexing finger. It's part of ASL determiners. The little square depicts a possessive pronoun in referential space. The little triangle symbolizes reflective pronouns such as itself, himself, and herself.
Another written piece below demonstrates another example of a ranking and listing grammar in ASL, using the reference system in ASL writing.
The spatial reference for ASL writing in these examples can be applied to many different possibilities in ASL writing.
The spatial reference system above is just a propositional idea. It may have its pros and cons. For example, a plus for shorthand and a minus for visibility.
Adrean Clark suggested another version above based on her instincts. She uses the existing pronoun symbols and rotates the pronoun symbol, pointing to different angles. Further, one can rotate to the left or right (45 degree and 80 degree). That would make at least four possible recycleable third-person or -thing referential space for pronouns.