@MushroomI have paused posting my "epic" story A Sixth Generation Cowboy and a Third Generation Whore; set in Colorado. I won't post until I complete the "first book" I have learned some lessons. One is that instead of trying to write such a huge story, instead write a number of shorter stories in a Series.
(I started writing before I knew about SOL. I started posting to get feedback, and to motivate me to complete the story... Then a heart attack, being forced into assisted living, no internet access for my laptop, Covid-19, etc.)
I have a number of short stories, never posted, many incomplete. I have been re-writing some. Sometimes I have altered the characters (some of whom were quite similar) to create several series set in different locations (Colorado, Washington State, Tennessee/Kentucky, Texas, and Florida). There are some significant similarities, so, I have plotted out some cross-overs.
Rather than "create" a new minor character, I am using one or more characters from another series in minor roles. It is not necessary for all readers to realize a minor character in a particular story may be a more important character in another story or series. These could be considered "Easter Eggs" but they make sense. Many of the characters are veterans of the US (and other) armed forces; quite a few participated in special operations. While more than 100,000 people have participated in "special operations" since September 11th 2001; actual "Operators" are a much smaller number. It is unlike that you'd "know" everyone. However, it is likely that you'd "know a Guy, who Knows a Guy..."
It is interesting that you posted this topic. I have recently been doing some editing to "insert" a couple of characters from one series into another story in a different series.