Something I've been wanting for a long time; take windows explorer for example. Say, there's a long list of files, and you want to find "fart123". So you click on the list and start typing "far" or whatever, and it narrows it down to that file. Another example is the font list on Photoshop.
Here's an example of me typing "nuke" to find Nuke Demo.bls in explorer (almost instant):

Here's me finding the same file, only in Blockland (about 5 seconds):

Please consider for the next update!