Hi @Prof_Techno, quite the diagram!
I couldn’t make out your scene because the screenshot resolution is too low (even when clicking « view original image »)
If I could give you one piece of advice, it would be to use the « Start scene » action which would allow you to split your large scene into small blocks, and thus factorize some actions:
For example, at the bottom of your diagram, you have cases that are always the same (target temperature reached or not → turning the pilot wire on or off).
Couldn’t this small block be its own scene?
One advantage of this strategy is that it lets you test each part of your scenes separately, and above all have smaller, more readable scenes.
Be sure to properly name each scene, with a description, and tags so you can find them easily.
You’re right!
On the « dashboards » and « scenes » views, we could increase the max-width.
I’ll look into that.
Edit: Discussion sur la largeur de la page "tableau de bord" et "Scène"
I think your scene is too complex; it should be split into smaller scenes in my opinion 
Don’t hesitate to create a feature request; I didn’t find an existing request on this topic, but it’s true that it’s not the first time we’ve talked about it!
Why not! Don’t hesitate to create a feature request