Hi Joe,
Right now the only way to "remove" a tool from the library is to just overwrite it with another tool definition by saving to the slot you wish to overwrite. There's not a way to blank out a tool library slot though.
I do think that for someone who uses PixelCNC the way you do it might be better to just use the new feature for loading tools from the library from the operation parameters interface. You don't need to have any tools defined for a project to create an operation anymore - though PixelCNC will still popup a messagebox about it, but it will still let you create a new operation and assumes you will be loading tools via the new "Load From Library" button that shows on operations' Tool parameter.
- Charlie