Functionally:
Fixed TabIndex (mostly by removing it), made the documentation link actually
visible, reordered the tabs, and changed some text.
In the code:
Did away with the designer's code style, moving declarations as close to their
init as possible.
To that end, most controls now use the object initialiser syntax, including
nested ControlCollections where possible (basically everything that isn't
assigned to a field).
The four TabPages and the more complex GroupBoxes are each constructed in a
helper method to make maintainance easier.
All event handlers are inlined as lambdas, the OK button's handler calls a
helper method to write out the config so it's easier to maintain.
Added some custom controls, and a float equality ext. method which I'm
definitely going to forget exists.