This is my working Blocky Event for my home ventilation system, level 1, 2, 3 and off.
Level 1 is dependent on bathroom or living room humidity.
Level 2 and 3 is dependent on bathroom humidity only.
Off only is only used when bathroom and living room humidity are below a set value.
I did not want the events to repeat over and over again. The value can maintain for hours and during this time the event is should normally be repeating every minute or so, that is why the event checks the current state of the switches. It only switches when the switches are in other state then the event puts them in.
I also wanted to have a manual button to set the ventilation manual on. I solved that by adding a virtual switch, that is not switching a real switch in the home. The setting of this switch is also checked in the event for level 1. Level 2 and 3 will set this switch to off. The manual 'on' setting will be reset if the humidity in the bathroom kicks the events for level 2 or 3.
Ventilation Off:
Level 1:
Level 2:
Level 3:
Result:
Most of the time, the ventilation is running on Level 1. During periods of dry weather, the ventilation stops completely.
When taking a shower, the ventilation is going to run on level 2, when taking a longer shower it even goes to level 3.
After a long shower it takes a while, then it goes back to level 2, then level 1.
I connected the home ventilation system with the 'klik-aan-klik-uit' switch type: ACM-3500-3 in front of the Perilex connector.
My ventilation system does not have a problem when level 1, 2 and 3 are powered up at the same time (or other variations) although it is designed to get power on wire 1, 1 and 2 or 1 and 3.
I have an Itho ECO-FAN CVE HP Perilex
Electrical scheme:

Because of warranty, I did not want to cut of the Perilex connector. But if you are able to do that, you also can use the switch instead of the perilex connector and plug. Then connect the wires from the fan directly to the switch.
In a normal situation, with a manual switch somewhere in your home, L1 will always be powered. You cannot shutdown the fan completely with this switch.
You can also choose to use a single switch within domoticz, to just add power to L2 (or L3) automatically. The fan is always running on level 1 and only when showering it switches to level 2 or level 3.
Makes it less complex when you don't want to shutdown the fan completely.
Electrical scheme for single switch, like KAKU ACM-1000:

(I did not test this one, but see no reasons why it should not work)