I just upgraded to 20.04. In the bottom left corner there is Show Applications which I also used in 18.04. I like to use it but there is a problem which has been around for a long time, and now I decided to do something about it.
The problem is there are a lot of "junk applications" which I would like to put into a folder which I can ignore. I've been looking how to do this. In 18.04 you can check applications and make a folder for them example
This no longer works in 20.04 as the check mark they talk about no longer appears. There is another program "meow" which also is supposed to work in 18.04. Only in 20.04 I just tried it and it too no longer works.
I made my junk folder, put some apps into it, and had a look. Under Show Applications the junk folder doesn't appear, so that apps would be gone forever. So I decided to delete the folder. The apps came back, but the predefined folders which were actually quite nice were also gone. Each icon now appears at the top level.
What is even worse is that some apps appear twice. System monitor, which I do use quite frequently now appears twice.
The basic question is first: how do I clean up the mess? These things are presumably in some system directory somewhere, so if I could clean out that directory, at least I could kill the duplicates.
Second, how do I now make my new directories, especially the junk directory? Junk are things I rarely if ever use, not things I want to kill without mercy.
20.04 does look nice, but I need to get some control over it.
gsettings get org.gnome.shell enabled-extensions gives output of: @as 
I also got some hints on why System Monitor appears twice. In usr/share/applications there are 2 desktop entries: gnome-system-monitor.desktop and gnome-system-monitor-kde.desktop
On my 18.04 computer there are the same 2 entries, but 18.04 shows only one of them in Show Applications. If there is no better solution I can delete the kde version in 20.04.