How do I open up the transaction dialog popup in Ardor Ignis via the URL parameters when the wallet gui loads in the browser?
I don't think there's a way to open up popups using just the URL, because it's not built inside the codebase.

The only reason you were able to go to a specific page was that there's a loader function for that page.

For instance, loadAssetFromURL() for the asset page in ardor/html/www/js/nrs.assetexchange.js