A couple of years ago @KKnBB created a utility to do this, but the link no longer works. Also, several people couldn’t get it to work as it required Admin privileges to install, which they did not have, while several others said their anti-virus prevented it from running. Also, if you wanted a different font, you had to edit the resulting.mlt file.
So, since I am needing something like this I decided to create my own utility. I’ve done it as a web utility - it is a single HTML file and it has a nice interface (see below), where you can tailor all of the parameters. I will use it in conjuction with my web utility Subrip (.srt) Generator, that will create the .srt file and the new utility will hardcode (burn) the subtitles into the video.
If you atre interested in using these utitlities, the .srt file generator can be found here: SubRip SRT Subtitles Generator (elusien.co.uk) and the SRT to MLT converter can be found here: Resources for Shotcut (elusien.co.uk). Both utilities can be downloaded (they are each a single HTML file that you run in a browser) and run locally without needing access to the internet.