Solutions as presented by Archwiki - this is a mere recitation.
In short the nm-applet package cannot be removed as it is essential part of cinnamon but you can suppress loading it by creating a custom cinnamon configuration.
cp /etc/xdg/autostart/nm-applet.desktop ~/.config/autostart/nm-applet.desktop
And append the line
You can make your screen "blink" by refreshing it.
for (( i=1 ; i<=5 ; i++ ))
xrefresh -solid blue
xrefresh -solid red
xrefresh -solid green
This should get your attention and get you in the mood for some epileptic dancing. Tune it up or down to your liking or just use part of your screen (-geometry option).
First, find the keyboard shortcuts menu. I don't have linux mint available, but according to this blog post it's a matter of going to Menu → Keyboard → Shortcuts:
Find 'Custom Shortcuts' in the left bar, and add one with the command xdotool type '¯\_(ツ)_/¯'. In 'Keyboard Bindings', bind it to a key (combination) of your choice.
Of course, there are many ...
I also struggle with knowing which window has focus (irrespective of how it got i).
I have switched on the glow feature of oxygen theme in KDE's plasma. I now have a different glow around active and inactive windows. I also set a matching title bar colour. Green for active, and red glow / gray title bar and border for inactive (but the borders are very thin)...