When looking for synonyms for the phrase "trivial matter," there are a number of options to consider. For example, instead of using "trivial," which implies that something is insignificant or unimportant, you might use the word "minor." This term suggests that an issue may be of some concern, but is not significant enough to be a major problem. Other similar phrases may include "petty" or "insignificant," both of which convey a similar sense of something being unimportant or unworthy of significant attention. Ultimately, the choice of synonym may depend largely on the context and intended audience, as well as the specific nuances of the situation at hand.