Chromium based browsers also have a similar feature under the "Manage Search Engines" settings (Took me a while to find this after I switched to Firefox)

I personally use short keywords like "ccc Lego" to search CamelCamelCamel or "e Razer" to search eBay

One thing Firefox does make trickier is that it doesn't make clear you're searching your custom search engine. Chromium recognizes my "ccc", so once I hit space it replaces it with "Search CamelCamelCamel: Lego". Firefox just leaves the bar "ccc Lego", makes it tricky to know if it recognized it.