I found this guide https://itsfoss.com/ubuntu-mate-customization/ where, regarding to this doubt I have, it says “Right click on any applet on the panel. You will see a popup menu. You can move any applet on the panel or remove them from there. Some of the applets also have additional options — like Edit, Preferences etc. After you are finished with the adjustments, you might also want to lock them to the panel.”
But in the new version of mate (1.20.1) I can’t find the way to Edit or change the preferences so that I can, for example, remove some of the elements (sound, network, session or any other) which are part of the indicator mate applet.
Yes. Darn right it’s by design. It seems to be part of a trend to forcibly remove decisions from the user and give them to developers. It reeks of “Microsoft WinThink”.
Well, I wrongly thought that I could edit the indicator applet when I used Ubuntu 16.04. My memory failed. In addition you can make some indicators to disappear from the Indicator Applet just by disabling them from startup graphically through "mate-session-properties", or creating a .desktop file in ~/.config/autostart
Personally I didn't want to have the session indicator so I take a look at this file /usr/share/mate/autostart/indicator-session.desktop to prevent /usr/lib/x86_64-linux-gnu/indicator-session/indicator-session-service to start with mate session.
16.04 did not have indicator applet. It used the tried and true Notification Area applet. In 18.04 you can remove the indicator applet and use the Notification Area instead. Look under System Tools in the menu and see if you have the dConf Editor. If not, you can download it in Synaptic or in a terminal by typing
sudo apt install dconf-editor
Once you have it it should show up in your System Tools menu. Run it. Click the search icon (a magnifying glass). type in
enable-sni-support
A button to turn sni support on appears. Turn it on. Now you can remove the indicator applet from the panel and add the Notification applet back. And now you are rocking just like you were in 16.04!
