Hi there, you are welcome to the Microsoft Edge Insider Community Hub!
The contextual search is available now in the stable channel. You can do that by double-clicking a word or selecting a phrase, right-clicking it and selecting the "Search the web for..." option. The contextual search will be greater with sidebar search which would search your word or phrase and give results on a bar on right side of your page in the same tab.
(Note: Sidebar search is only available to Insider Channels in CFR and would be coming to the stable channel in foreseeable future.)