I use a unique numbering system for some of my lists for tracking purposes. I use a unique ID for the department and the List. So if I was building a IT Request, I would mark the first three characters with a ITR then I would add the calendar year (or fiscal) then I would add a 4 digit number that increased each time a new item was added to a list. So the number would be ITR-2020-0001. I set up a variable list to pull from in SharePoint/O365. I have attached my workflow to it for an example.