It is totally getting on my nerves, I have crazy long passwords, and it is almost impossible to write it there correctly. I dont know what is wrong. I hope in NEM client it will be allowed to just copy password in wallet or it will be huge turn off.
Looks like you are using Wallet app. You need to upgrade it to 1.2 http://nxtra.org/nxt-wallet/ (right click issue was fixed)
If you don't do that, while the client is running, this URL should work too http://127.0.0.1:7876/
It will open the client in default browser and right click should work there.
By the way, Ctrl + V still works for paste.
In any case, don't use notepad. Use something like Lastpass https://lastpass.com/