OK, so after experimenting further I think I've found a workaround.
It is long winded compared to the previous workflow, however it's better than scenery creation coming to a grinding halt.
1./ First of all copy your latest compiled package into your Community folder
2./ Create, or amend your custom objects and compile in the normal way in Blender, 3D max, etc
3./ Run the sim and once in the Main Menu open your project and 'Build Package' (no need to go to your airport in the sim at this stage to save time) DO NOT click Load In Editor at this stage.
4./ Once the package has been built, exit the sim.
5./ Go to your project folder, copy and replace the previous compiled version into your Community Folder.
6./ Run the sim and go to your airport/scenery area, then open your project, myscene and click 'Load In Editor', DO NOT click Build Package.
7./ Your new, or amended asset should now show in the Objects of the scenery editor
I hope this helps and works for you. Hopefully there will be a proper fix soon!
It is totally logical, that if i put something in the community folder, that all that stuff will appear in the simulator, because that's what it's for, to put the finished build package in the community folder to be used. This is definitely not a creative, logical and productive workflow at all, to constantly create a finished package after each little change in the project editor, push build, copy the finished package to the community folder and restart the sim - because otherwise new and changed stuff won't be recognized by the sim, unless freshly started ! This takes the fun of creating an addon for me ... i'm not willing to go on creating something, if it can only be done like this anymore ... i'm not paid for what i do ... so why wasting 10 times the amount of my free time, trying to create something now with this crazy changed. process.
When i was working on projects the whole time, i never cared about the finished package of my project, until it was all complete, working and done. After all the changes, small or large, i've erased the packages and package_int folders, to just close and open the project again, while the sim was running all the time - no need to restart the sim at all. I don't even want to think about it, if this would have had to be done the whole time before - all those small changes i've made on my Blender models for instance, i was able to check them instantly just by closing and reloading the project or even just copying the changed exported files over the old ones and watch in realtime my models change and show the effect. And i can clearly say that i would have never started to create addons, because this would have been way to painful and time consuming, to go on or even starting a mod and waste my free time.
It might be not a problem, to use this for adding a few lights here and there - but to create new objects in a software like Blender, you need to be able to view the changes rightaway and fast in the sim, because whatever you see in Blender, whatever a gltf-viewer will show, is not exactly that, what will happen with this object inside the MSFS, which has extra special rules, to display those objects.
And i believe that because of the ease of use of the editing process like it was before World Update 4 , all those mods, addons, got created. But if the editing process would have been this crazy working like that right from the release of the sim, i bet, there would have been just a smalll fraction of modders willing to go through this painful creation process and just a very small fraction of addons would be available now.