So, gathering all the feedback and my own tweaks, I finish with the attached (merely simplified). -- Michael
+1 As an end-user, It it is very clear for me now.
Verified the new example : $ psql "postgresql://user@localhost:5433/mydb?options=-c%20synchronous_commit%3Doff" Password for user user: Pager usage is off. psql (12.0 (Ubuntu 12.0-2.pgdg18.04+1), server 11.5) Type "help" for help.
mydb=> show synchronous_commit; synchronous_commit -------------------- off (1 row)