The joint track editor is used for editing how joints should move in the current scene. To actually specify the joints in your model, you need to go to the object tree panel and define joints there first.
Calculate tween values and update the scene.
After this button is pressed, the tween values for all the joint tracks are recalculated and written to the frames. You get the best idea of what the effects of your changes to the joint tracks are when you view the animation during the changing and updating of the joint tracks.
The first button will change a selected range of cells into key values. The second button will change the selected range of cells into tween values.
In the grid you can see the difference in tween values which are gray and key values which are black. The key values are the only ones that can be changed the tween values are recalculated after you press the update scene button.
The first button will make the grid cells more narrow and the second button will make the grid cells wider.
A joint track is a sequence of values that specify the position of a joint in a sequence of frames. It is represented in the joint track editor as a horizontal row in the grid. For a joint track you can specify key values in the sequence that you wish to set yourself, and you specify the rest of the joint track as tween values to be calculated as a linear interpolation by qME.
In the grid you can select multiple cells with the mouse by dragging or with the cursor keys when you hold down the SHIFT key. Then you can press either the "Mark as Key Value" or "Mark as Tween Value" button to turn the selected cells into key or tween values.
For key values you can change the values in the grid by double clicking it and then typing in new values. When you have finished with filling in the key values, you press the update scene button and the scene will be updated with new values for the joint track after the in-between values have been interpolated.
I usually have the animation playing in the frame editor when I edit the joint tracks. This allows me to view the animation changing during the editing of the joint tracks.