Currently Orion does not support direct search in the address bar via "rd <keyword>".
https://help.raindrop.io/browser-extension/#search-from-address-bar
I asked the developer of Raindrop about this feature:
"Probably Orion doesn't have such feature for extensions"
Orion 0.99.127.1-rc (WebKit 619.1.1)
MacOS Sonoma 14.4.1