This tiny extension replaces the embedded browser dialog for editing existing about:config parameters and creation of new ones by a much more convenient window - resizable and multi-line:
Apart that, creation of a new parameter is no more a two-step operation: in the new window you can enter both parameter name and value:
Moreover, now you can copy an existent parameter and paste it into any input field in a form used by the browser itself: parameter_name;parameter_value. After pressing "OK" button, extension will parse the pasted string, split it, and fill input fields properly:
The home page of New Preference Editor is http://yup.lh1.in/AddOns/NewPrefEditor
Also it should be available soon at https://addons.palemoon.org/addon/newprefeditor/