Now you have a humidity sensor in the bathroom maybe add a smart switch for the fan. You then can use my 
Bathroom Humidity Exhaust Fan blueprint to turn the fan ON and it will also keep the lights ON. In the FAQ of that blueprint I show my full set up and how I do it.
You could also us a door contact sensor so when you are in the bathroom and motion is detected it will keep the light ON until you open the door. To do this I have developed a template sensor called 
Bee In The Hive Sensor and this shows you how to do it, click here. This way when you are behind the shower curtain it will keep the lights ON.
Personally I use my Bathroom Humidity Exhaust Fan blueprint with this blueprint to achieve everything.
This would be done by using night lights and using night light time option and set when you would like the lights at 50% so from 17:00 to 07:00. Then set up your night lights.
Hope this helps you.
Blacky 