1. Add the ability to drag the column divider to adjust the width of the area where custom guides are listed
2. Add the ability to sort the list of custom guides (e.g., a sort button at the top of the list)
3. Add the ability to drag any custom guide title up or down in the list so you can reorder them with your favorites at the top. [Yes, as a hack, if #2 were implemented, we could rename them with numbers before them so they'd sort in the order we want, but this would look cluttered and would be cumbersome to reorder/renumber them all if you created a new guide that you wanted to position somewhere near the top of the list.]
