EDIT: Updated picture, plus more answers.
Rotate Pivot: Sometimes you want to have the Pivot aligned to/with your objects instead of Worl, which is default when you drop an object on the canvas. Here I draw a Line (selected, and the Pivot is aligned to World), and a Point on left side on the line, also World.
Now to rotate the pivot for the Line (attention, not the point in the square)): The RotatePivot command is found only on the Properties-Panel Menu (not on Bongo’s main menu, as irritating as it is…),
… and no to rotate the Point’s Pivot, and then it looks like so (first reference point = along World X).
Make sure you do not use Perspective view when rotating the pivot, the Rotate Pivot command will most certainly fail if you do. Use Top/Front/Left/Right views, only) :
… then click in the align direction :
… and so the Point’s Pivot it is aligned after clicking in the desired direction :
(Sorry, had the wrong picture, now updated)
This kind of alignment is required if you for use Telescope in a non-World direction, for example.
[quote=“Andrew_Nowicki, post:1, topic:44069”]
What is the purpose of (undocumented) BongoPivotLock command?[/quote]
I’ve never used that one, don’t know.
[quote=“Andrew_Nowicki, post:1, topic:44069”][
What is the purpose of (undocumented) BongoCopyChain command?[/quote]
Just a kind of “wizard”, it does only what you would do your self manually, if you do it in the “right order”. I never use it, because I think in arbitrary order and so… a link here and a link there is just as good. 
At least it ends up being the same thing at the end of the day.
[quote=“Andrew_Nowicki, post:1, topic:44069”][
Can Bongo rotate object about arbitrary line?[/quote]
This is where the Pivot comes in. You can rotate any object at any position. But this means that you need to move an object’s Pivot to the position where you want to have the “hinge” (and sometimes you would also like to align it,. but as said, only if you plan to slide along something).
Typically a line-end is a desired pivot/hinge point, but you can place the pivot anywhere on a Line/object. The just type in your rotation values in the keyframes.
[quote=“Andrew_Nowicki, post:1, topic:44069”]
Green keyframe markers represent document keyframes. Margaret told me that sun position is example of document keyframe. She promised to explain document keyframes in the help file, but she did not. Do you know more examples of document keyframes?[/quote]
I’ve never used that one, but I recall how puzzled I was before I could see object properties in the Keyframe editor (the sun is an object just like any other object in that regard). So I came up with the idea to start with selecting ALL the objects I plan to include in the animation, then click Move Pivot - but I’m not actually moving anything, I just click the “Reset” option on the command line that shows up, and confirm with RETURN.
This will make all the objects show up in the Bongo Tree View. I use to use that one for naming objects and keeping a structure even when NOT using Bongo for animations…
Hope this helps you to proceed.
// Rolf
I am surprised by the quality and speed of your response. I believe that McNeel should pay you top-level salary for improving Bongo help file.