Documentation on New Timeline 4.12.0.86, TCB

Constance1

Is there any documentation on the new Timeline in 4.12.0.86?

Specifically: what does the "TCB" do? I see how to select some keys on the TImeline by dragging a box around them, but then what?

Richard Haseltine

This is the link I was given when  asked about that https://en.wikipedia.org/wiki/Kochanek–Bartels_spline