Hi and welcome back 
if a variable does not exist, you can simply create it via “ucr set”:
ucr set connector/ad/mapping/computer/syncmode=none
The reason why the connector variables are named a bit strange is the following:
It is possible to run more than one instance of the Univention-AD-Connector on the same host (not via the UMC module, needs to be configurde on the shell). This way UCS can sync with several independent MS Active Directories:
+-----------+
| |
| UCS |
+--------> <---------+
| | | |
| +-----------+ |
connector | | connector2
| |
| |
| |
| |
+------v-----+ +-----v------+
| | | |
| | | |
| AD 1 | | AD 2 |
| | | |
| | | |
+------------+ +------------+
The first (default) instance is always called connector but the second can be named as you like as long as it starts with “con”. The “con.*” you see in the UCR variables is just the corresponding regular expression to make this work. Think of it as a placeholder.