Recently had a case in hand to auto-fill a large multi-page form in a SPA for quick tests. This was a repetitive task so it made sense to have a script for it. The script had to be injected locally on my browser which then filled-in the form based on the type of fill that I selected. I achieved this by adding a bookmark to open a popup which then displayed different buttons for various type of auto-fill I needed.
Setting up the browser to open your popup.
This can be achieved by using the following as URL for the bookmark
bookmark.js then uses document.write to populate html, auto-fill scripts on the popup window.
Note: I have used https instead of http as mordern browsers block/disable popup or its contents if the source is not over served over https