Steps to reproduce:
Launch Orion, close all Orion windows without quitting the app, select a link to a page either (a) from the Orion browsing history (menu "History"), but only from the top list, not from any of the older links in the subfolders, or (b) from the "Bookmarks" menu in the subfolders "Favorites" or "Bookmarks Bar".
If there is no open browser window present, I expect Orion to create a new window with a blank tab, and open the URL selected from the menu "History" or from "Bookmarks Bar" or from "Favorites". Instead, nothing happens. However, if you select a link from one of the subfolders in the "History" menu, e.g. from the dated subfolders or from the "Recently Closed" subfolder, Orion actually does create a new window and opens the link there, so this functionality has been partially implemented.
So I assume that this is a bug, since that behavior does not work in all cases.
Orion, OS version; hardware type:
0.99.124.1-beta (WebKit 616.1.10)
Intel MacBook Pro 2018
macOS Ventura 13.4