It's as simple as possible but no simpler (with apologies).
There are no words to express how helpful this add-on is.
The only problems I've found are of my creation!

Simple to set up. Simple to use. Perfect! Just what I was looking for. Can set up any string of characters to be saved in the add-on for use on any form.

hallo.
ist gut.

Functional and easy to use with basic options. Certainly better for users than developers.

Hi,
Thanks for reply, but you are taking it wrong.

I am asking you to provide an option of completely remove 'Simple Form Fill' from the context menu (not a single item):
https://addons.cdn.mozilla.net/user-media/previews/full/184/184694.png

Currently this is visible even if you right-click on empty element of any website.

Nothing fancy like the form fill feature of LastPass but it does it's job albeit not as quickly.