"Of this" is commonly used to refer to something that is already mentioned or known. There are several synonyms for this phrase that can be used to add variety and precision to your writing. "Regarding this", "pertaining to this", "related to this" and "concerning this" can all be used to convey a similar meaning. Other options include "associated with this", "connected to this" and "in relation to this". Using different synonyms can also help to clarify the context in which the phrase is being used, making it easier for readers to understand your meaning.