Fixed a few bugs, improved the interface and controls, and added a submode of "Swap tiles" which lets you insert selected tiles as new lines instead of swapping them with other tiles.
Version 1.1 adds a new mode: cut and insert whole rows. It also draws black and purple squares over any tile which is fully transparent to make them stand out more, as they're likely to be unused blank tiles you should delete.
It is now also compatible with Essentials v20 and v20.1.