Hold control and right-click the sewing kit to get to the new user interface. I believe there is a button in the new tradeskill UI that asks you if you want to open the new UI or the classic "experiment" mode, check or uncheck that.
In the kit is a button the says something like "open with ctrl+r click". Press that button and the kit will open normally with a right click and in tradeskill mode with a ctrl+right click.
Much easier that way since I use it as a container more than a tradeskill item.