What's the use case? The reason this doesn't exist in Zotero Desktop is that importing from the browser works via the browser connector works better in a number of ways.
Not always. First, some users are not allowed by their employers to use the browser connector. I have to switch back and forth between my government computer (not allowed to use browser connector but I can use Desktop and ZoteroBib) and my personal computer, emailing URLs from one to the other. Took me years to get my agency to allow Zotero Desktop. The next use case is when one has a list of several--or many--URLs to add. Third, the URL lookup often gives better results (in ZoteroBib) than the generic read gives. Don't know why, but it does. Many generic web pages load as page title and URL, with little else. Using the URL lookup in ZoteroBib usually finds the date and the site name.
Third, the URL lookup often gives better results (in ZoteroBib) than the generic read gives.
By "generic read" you mean the Zotero Connector? ZoteroBib (or adding by URL in the Zotero web library) should never do better than the Zotero Connector. They're using the same code (with ZoteroBib behind, if anything), ZoteroBib runs server-side and is far more likely to be throttled or blocked, and ZoteroBib doesn't have access to proxied sites. If you're seeing better results from ZoteroBib for some site, you should report it as a bug.
And it would be the same with in-app URL lookup. It would be the same or worse than the Zotero Connector, and usually worse. You wouldn't get a snapshot or PDF for any site that required a login or web-based proxy access. And some sites that people save to Zotero are entirely gated. We're not particularly inclined to add this and make it seem like a recommended way of adding webpages to Zotero when there's a way to get vastly better results.
Having some way to support web-based proxy access within the app would help, but that's hard to do on a technical level — basically, we don't have a good way of knowing which web requests should go through the proxy and which shouldn't, and we can't just blindly send all web requests Zotero makes through the proxy. And proxy support still wouldn't solve problems with other sites that require login.
I have to switch back and forth between my government computer (not allowed to use browser connector but I can use Desktop and ZoteroBib) and my personal computer, emailing URLs from one to the other.
FWIW, the Zotero web library has the exact same add by identifier function as ZotBib, including URLs, so you don't need that workaround.
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And it would be the same with in-app URL lookup. It would be the same or worse than the Zotero Connector, and usually worse. You wouldn't get a snapshot or PDF for any site that required a login or web-based proxy access. And some sites that people save to Zotero are entirely gated. We're not particularly inclined to add this and make it seem like a recommended way of adding webpages to Zotero when there's a way to get vastly better results.
Having some way to support web-based proxy access within the app would help, but that's hard to do on a technical level — basically, we don't have a good way of knowing which web requests should go through the proxy and which shouldn't, and we can't just blindly send all web requests Zotero makes through the proxy. And proxy support still wouldn't solve problems with other sites that require login.
More on this here: https://forums.zotero.org/discussion/comment/337643/#Comment_337643