UE4.21 Bug Report - Impossible to add new leves in the level editor for streaming, why?

Hi, i can´t add new levels to persistent in level menu after click “enable world composition”

I actually followed a YouTube tutorial, so i know something is wrong, I clicked “enable world composition”, then opened the level menu wich shows the “persistent level” in light blue color, But now, if i click levels/ create new, a window appears, i create the new level, and it does appear created into my folders, but it doesn´t show in the level editor, i also tried to drag them to the level menu, under “persistent” but it also desn´t work, is this a bug in world composition?

Please help!