Help & troubleshooting for channels on your Roku device, including adding/removing channels, logging in to, authenticating, or activating a channel, channel-specific playback issues, assistance contacting channel publishers to report issues, and adjusting channel-specific settings.
Go into the YouTube app, left arrow to the column of choices, down arrow to "Settings", Then down Arrow to "Clear search history". This worked for me, at least when signed into my account. It should also work for "Guest".
Now the hard part: how do you SAVE a search. If I search as "Guest", it puts that into the list of saved searches, so I can re-find my favorite channels and topics. But if I search while logged in to my account, my searches are NOT saved. All I see are YouTubes force-fed searches (with the little odd flame icon), and they are never replaced with my searches. Does anyone else see this, and do you know how to put your own searches there?
Thanks for letting us know about the issue that you are experiencing.
For more information about that channel's features and functionality, you'll want to contact Youtube support directly to inquire further. Many channels on Roku are developed and maintained by the channel provider themselves.