jks123
A "double space" character (if you mean it) does not exist. If you want, you can already choose "Tools | AutoCorrect Options" in Atlantis, and add the following "replace with" pair:
replace ".<space>" with ".<space><space>"
In this way Atlantis would automatically add one more space after the last typed sentence.
replace ".<space>" with ".<space><space>"
In this way Atlantis would automatically add one more space after the last typed sentence.