I am using the "Most frequently used nodes" very often. As in my case it works nice to take the 50 most used nodes, it is a bit cumbersome to find a node if it is not at the top somewhere. As the order of the nodes keeps changing (dependent on their usage), I cannot rely on remembering the approximate position in the list.
I would find it very helpful if there would be such a little search field like in the node repository. (In the node repository it tends to get slower and slower the longer my KNIME stays open)