When I update the list (with next new leader release) I will include a new column on the right listing the Civ 5 leaders in the centuries they appear. I've only just started on this part, and Theodora's Byzantines and Ramesses II both would expand the coverage of the Civ6 list.
Maybe someday the community will have the tools to mod in as many leaders as we want but for now this chart can only serve to show us what's covered and what's missing. I do use it myself I had a blast on a large world with the leaders all from Seondeok - Genghis Khan span of years, which is 5 centuries sure but you still have 8 leaders from the years 1046-1284.