@Moolissak
Go to the Search on your Home Screen. After you select it, you should see the image posters on the right under "Recent Search Selections". Scroll through it a bit to the right (to the end number of your searches) and you should see a little text poster/tile that appears and says "Clear All". (kind of wedged between the image posters so easy to miss).
There is another section labeled "Based on Your Recent Searches". Unfortunately, no way to clear that one yet.
Roku Community Streaming Expert
Just another Roku user... I am not a Roku employee.
Insignia RokuTV, Ultra 4660, 4802, 4850, Premiere+ 3921, Express 4k+ 3941, Streambar 9102