I found a project backup I made before messing with the settings with the right default values, now everything works as usual.
Some day I need to dedicate a few days for experimentation about display settings. It’s fundamental for my use of Unreal (mainly presentations with notebooks attached to projectors or big screens). But, for sure, I’ll do those tests and “crash learning” out of any commercial project with delivery deadline…
I tested Unity for a few days before I decided to stick to Unreal. With Unity you can very easily handle a 2nd monitor (or projector, whatever you plug in the HDMI output). For instance, send to that 2nd screen a render with no HUD or mouse. I mean, the presentation host has all menus and mouse in his laptop while the audience only sees the clean result. Being able to do that with Unreal would be FANTASTIC but I’ve found no way to do it with Blueprints. Some day I’ll open a question about this.
Thanks again tuerer. Your comment to my question was the right answer. Promote it to answer and we van close this newbies thread.