Can you show me how you made your scene? That will help to better understand, it might be a bug.
Indeed, unfortunately it’s not automatic. Ikea ones, for example, are ultra-basic.
I recommend my current smart plugs: https://www.domadoo.fr/fr/peripheriques/6165-nous-prise-intelligente-zigbee-30-mesure-de-consommation-5907772033517.html?domid=17
No — when you delete a scene, there is no longer any action on the device you want to control.
So if you turn on a plug and then delete the scene, well, the plug stays on, nothing surprising.
I also use @lmilcent’s take, and it’s not bad.
@_Will_71 Thanks for your reply. So you confirm what I thought yesterday.
That there wasn’t, by default, an « off » command sent after deleting the scene.
@lmilcent Thanks for the plug reference. 
I had picked this one to start with.
https://www.amazon.fr/gp/product/B07SFZ81SK/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8\u0026psc=1
Okay, I managed to filter and turn it on depending on the days, so that’s good.
Now I have to figure out how to turn it off at a set time. 
I’ll end up going to read the scenes’ config files directly if this keeps up.