When it comes to finding synonyms for the phrase "in that matter", there are several options that can be used in its place. One alternative is "in that regard." This phrase means the same thing, referring to a specific topic or issue. Another option is "in that vein," which is often used when discussing related or similar subjects. "In that respect" is also commonly used, particularly in formal settings or academic writing. Other possibilities include "on that note," "to that end," and "concerning that issue." Regardless of which synonym is chosen, each one helps clarify the subject at hand and provides a more precise way to convey meaning and intention.