As @sparkydave suggested it would better to use another automation for this. This blueprint is very complex and to add a feature like this would make it even more complex.
The good news is I already have another blueprint that will do this and it is called 
State Notifications & Actions. Your trigger would be when the fan turns ON (in the start trigger). Then in the start notify add your device. In the Global conditions add a condition for entity, state, add your window sensor with the state OFF or closed.
Now when the fan turn ON and your window is closed you will be notified.
You also have so many more options in this blueprint like actions. You could also use the actions so your lights flash ON and OFF say 3 times if the window is closed. You can use notify and actions or rather than send the notification you just use the actions so whoever is taking a shower can just see this visual.
Blacky 