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
In most cases you should use the unconfirmedBalanceNQT. Think about it as spendable balance i.e. your total balance minus coins/asset shares/currency units locked for various reasons such unfulfilled coin exchange orders.