Rated 2 out of 5 stars

useful tool, but I don´t understand why the developer did it that way

alt+shift+C for paste ??
Why not ctrl+c

Why is is not possible to paste all files from the clipboard?

If that this get changed, it will get 5 stars

This review is for a previous version of the add-on (1.0). 

You probably meant Ctrl+V (Paste). This binding is obviously already taken by the regular paste function. Ctrl+Shift+V is also taken by "Paste without formatting". I figured the next best thing would be Alt+Shift+V.

Pasting multiple files is currently not possible due to Thunderbird API limitations.