Hi there,
First, you’ll need to host your widget somewhere. We use GitHub Pages and it creates a URL for the repository.
Then, when you’re configuring a custom widget either at docs.getgrist.com or when using Grist-Electron, you’ll enter the URL rather than selecting a pre-made custom widget.
For example, I have a custom widget to view URLs, hosted on my personal github.io repository.
The URL for this widget would be https://nataliemisasi.github.io/URL_viewer
If I enter this as the custom URL for the widget, I can then configure the widget and then view the website at the URL listed.
Thanks,
Natalie