How to create a Total Visitors metric to identify all visitors

I hope I understood your question correctly. But technically the unique visitor metric is counted only once, regardless of how many times they visit the site. So if a user returns to the site multiple times, they are still counted as one unique visitor. 

If you create a segment for returning visitors based on visits greater than 1 (eg. Visits => 2), those users will still count as unique visitors because they are included in the unique visitors metric. But you will see how many of the unique visitors have actually returned (within a date range).

• Visit 1:

  • A new visitor accesses the site
  • Unique visitors count: 1 (this is the first visit)

• Visit 2:

  • The same visitor returns to the site.
  • Unique visitors count: Still 1 (they're counted as the same unique visitor)
  • Returning visitor count: 1 (they are now identified as a returning visitor)

Not sure if this is what you were looking for. I hope it helps!