Just be aware; also in the CVL itself, tracks have a initial set direction.
Rewriting the CTD file will allow you to make an activity (or use the network in explore mode) with driving on the left, as the CTD file will tell te CVL to set paths with a certain direction when trains are detected in certain blocks. However, when you start an activity with trains already present on the whole network, you will find the CVL might not accept the commands from the CTD file.
Let's say the situation below (image) is the situation at the beginning of your activity, with a CVL that has been build for right hand traffic. You have written a CTD file which tells the CVL to make a path for train A, to go from block 201 to block 102, in order to depart the begin station and enter the line on the left side.
The CVL will not allow this path, and therefore does nothing. Why not? In order to make this path, the CVL needs to set the driving direction of all blocks on that track until the next junction (blocks 102 - 111) in east-bound direction. But it can not do that, as the initial settings of the CVL have this track function west-bound, and there is already a train on it (train B). As long as that train is there, the CVL will not allow changing the track direction.
Now, you might have activated train B to want to run east-bound when the activity begins, but it will not move now. Why not? The initial direction of that track is still west-bound. And so, the east-direction activated cab of train B will not get an ATB signal higher then "10-absoluut", and therefore it won't depart.
So, in order to set the tracks for left-hand traffic, train B can not be there at the start of the simulation.
When I build a Simvliet left hand traffic activity a few years ago, I managed to get it to work as the junctions in Simvliet are very close together.
In Rijndam, it only worked for me for line M1. I could not get it to work in M2/M3.
If you want it in Rijndam to work on the entire network, you should perhaps do a "Weekday" activity; initial situation; an empty network (so no initial track direction reversal problems), and then start service by having trains exit the depot.
