Believe it or not. I used the power of talking to one of my characters - Nate Lukas - to solve this Google Docs problem with one of my manuscripts I had. Yes, it is a well known "self-help technique" to have imagined consultations with heroes and experts. And I talk to all of my characters all the time.
Mind you nobody at Google support could help (after 3 online chats and waiting for ever!) and there was literally no solution online about "how to add space after a full stop in Google Docs".
After a week I finally decided to ask Nate Lukas how to solve this. And today I actually found out how it works:
Read the full details and who the real person was that gave me this solution: