Maybe this kind of tools that help generating ready-to-use HTML overlays should not go into Shotcut since they answer very specific needs, but instead having those tools referenced from a page on Shotcut page would help users. So if someone has a specific need, it would be possible to quickly check if a helper is available to create the HTML. Since not every video editor is a web coder, this could be useful. But maybe this already exists. Does it ?
This being said, i think Shotcut would benefit at introducing a new file format with a specific extension, that would group all the HTML resources into a single file, like a ZIP archive that would contain: the HTML file, the associated CSS, JS, images, fonts, …, and maybe a webvfx.js file to ensure compatiblity. That would make FX much more portable than it is now. For instance, in my tool, for making things easy for users and have only one file to manipulate, i had to data-url-encode the image into the HTML file, which had as a side effect to break jonray’s notepad editor.
Even better, if that FX file format publishes a manifest that defines parameters for the given FX resources, Shotcut could provide the UI to edit those parameters and customize the FX. Like someone would write a “Credits” FX resource and allow the user to edit the credit text and background color directly from within Shotcut. But again, this may already exist and i just missed it.