I've been waiting for this for many years!

Terrific! I waited this possibility for years!

This is a must have gmail addon. We couldn't do without it.

I am so very happy I have discovered this. I have no idea whether it is going to be buggy, etc - what I do know is that it finally allows me to master my inbox, showing me notes on top of subject lines WITHOUT MY NEEDING TO OPEN MAIL! So easy and convenient.

This is by far the best extension I have used for this. I use it constantly and will even pay for it if I needed to. Under active development which means that any bugs get fixed quickly.

Great app, excellent support. Keeping up with browser and gmail changes is not easy. Invaluable app for the way I use gmail.
Now end-March 2020 - still invaluable to me.
Firefox required the developers to jump through hoops recently on security and other issues. No problem.

This is something what should be in every email client by default! Extension is even more important, if Google is closing Inbox, which have similar functionality.