Go to chrome://settings/searchEngines, click to add a custom search engine and add search engines with short keywords. For example you can add "https://www.youtube.com/results?search_query=%s" with the keyword "y", then if you type "y whatever" in the omnibar it will search "whatever" on youtube. The big draw back is that you won't get search suggestions when using a keyword.

Here are my most used custom search engines:

w https://en.wikipedia.org/wiki/Special:Search?search=%s search wikipedia using wikipedia's search engine

ww https://www.google.com/search?&q=site%3Awikipedia.org+%s&btn... search wikipedia through google and open the first result

h https://www.google.ca/search?q=site%3Anews.ycombinator.com+%... results only from hacker news

r https://www.google.ca/search?q=site%3Areddit.com+%s only search results from reddit

y https://www.youtube.com/results?search_query=%s youtube

b http://93.174.95.27/search.php?req=%s search for books on libgen

m https://www.google.ca/maps/search/%s google maps

wo https://www.wolframalpha.com/input/?i=%s wolfram alpha

ima https://www.google.com/search?tbm=isch&q=%s google image search (I tried using "i" and "im", but those are often part of my query)

s https://www.google.ca/search?q=site%3Astackoverflow.com+%s search stack overflow through google

st https://stackexchange.com/search?q=%s search all stack exchange sites through their search engine