If I install a ‘frontend’ resource using HACS and I want to work on making changes to that code -and- test the results in my Dashboard, is it as simple as forking the project on Github then re-directing the resource to the public URL for that .js file that is normally referred to as /local/.js?
You can just install in /YourHAConfigFolder/custom_components/FolderGoesHere for custom integration or /YourHAConfigFolder/www/YourCard.js for custom cards
Custom card must be added as a resource also
You can fork and install that or modify directly and install that