Does the job nicely, just what I needed and google for to my surprise for how few downloads it has! My only feedback would be a confirmation to delete a script or more promiment button styling to differentiate. I've somehow stumbled and deleted my main script a few times now.

Can run scripts on demand (pressing Run button). I use it to collect some info from the page and open an e-mail message and paste there, so I do not need automatic injection, but more control, and here is where Tampermonkey and ViolentMonkey failed.