Some browser extensions can be activated by keyboard shortcut, however many cannot. It depends on each individual extension. Take, for example, Zotero: This extension has one function (extract metadata from current page and save to the main Zotero application), which can be activated only by clicking on the extension icon.
I find the click-only approach to be unergonomic, especially if the extension is hidden in the overflow menu. (Sometimes I might be activating the Zotero extension 10 or 15 times in quick succession, and I suffer from RSI...) Chromium browsers offer such key mapping capability for most/all extensions. In Safari, UI scripting is required.
My suggestion is that Orion should add Tools > Extensions > [name of extension] > Activate to the application menu for each extension, with Activate effectively simulating a left click on the extension icon. This could then be mapped to keyboard shortcut using the system keyboard shortcut settings, or with a third party app such as Keyboard Maestro.
