How do you do a back up. And a back up of what exactly please ? Several times I've had to redo my bindings.
The Bindings are usually (unless you've explicitely moved them, and I wouldn't even know how to start doing that) in %LOCALAPPDATA\Frontier Developments\Elite Dangerous\Options\Bindings (on my PC, that resolves to C:\Users\markus\AppData\Local\Frontier Developments\Elite Dangerous\Options\Bindings - YMMV, but not by that much).
There should be at least one Custom.3.0.binds file in there - take it and copy it to a completely different folder on a different drive -
DON'T simply create a copy and rename it to something unsuspicious in the same folder as ED will scan also the header lines of all the files inside this folder.
If you're too lazy for that, install 7zip (alwys a good idea in any case), then afterwards right-click on your binds file, select 7zip -> add to archive... and give it a fancy name of your liking (or simply use the default name/archive). ED won't scan zipped archives, thank goodness, so you can simply leave it lying there.
Oh, and for those who claim to have lost their bindings: in the same folder, there's also a BindingLoadingErrors.log. Read it. Uusally, the bindings aren't lost, but someone simply misplaced one or more USB devices that were used in those bindings, which makes ED fall back to the basic default kb&m bindings. Check the error log and the latest binds file, it should still all be there waiting for the right hardware to be connected.
Oh, and ED will also have placed a few backups in there - supposedly every time it actually changes the bindings. Not counting my own backups, I have now accumulated a dozen binds files there.
P.S.: Make sure about the blanks in the paths - there's another pathe nearby that starts with Frontier_Developments - that's different stuff.