In UE 4.23 under Editor Preferences, there is a Checkbox: “Landscape Layer System” with which I can enable the new Non-destructive Layer System and the Blueprint Brushes.
Here a Picture:
I think it was transitioned in 4.24 to no longer being experimental. I seem to recall that being mentioned in the 4.24 release notes. Are you able to work with layers/BP brushes without the checkbox checked?
Yes. It is just not where the documentation says it is (not exactly). When you create a new landscape, the tickbox to enable layer editing is right front-and-center (as in picture) at the top of the options.
Ah, this explains everything.
My map has many sublevels and I had to enable edit Layers on the main Landscape, so all the landscapes in my sublevels are getting this also enabled.
Now everything works flawless, Thank you for your help!