For me (LM 21.3 MATE), I welcome the ability of Ayatana Indicators to retain a list of notifications that have come and gone. It is long overdue. But I am unable to configure these indicators. The Ayatana Indicators Settings app in the Control Centre is flakey. You can't change tabs with the mouse. You can change tabs with the cursor keys until you edit some settings on a tab, then you can't. The settings have no effect anyway, even after a logout/login. Major QA fail. On a minor note, the Time settings should include a 24-hr option.