I keep a Google Sheet with the DNA match information. The Google tools (Drive, Docs, Sheets, Slides, etc.) are free, so you don't have to pay for a license of Microsoft Excel.
I keep it private, because it has the names of my DNA matches, who almost all of them are living people. I have the abbreviation I use in the citations, associated with the DNA match. Along with a bunch of other data that allows me to either see the match details, or get to other match details.