First of all. What add and remove inbetweens do and why are so helpful for me.
The function is easy and maybe silly but I find it like a time saving tool.
It just add an inbetween or remove it from the space between two keys. Watching at it in the time line, we can observe how it moves all the following keyframes left or right. It could looks not much interesting but for me it is very helpful. I mean, when I have to check my timing, I select (with a script) all the controls on the rig and then, I play the animation and I add or remove inbetweens easily wherever I find it's needed. The way to do that is selecting the space inbetween two keyframes on the timeline and pressing the k or l key. (It is like + and - in flash animation)
(Pressing delete inbetwen all the following keyframes are moved to the left)
Well, lets go to check the hotkey editor. Its quite good to know how to use it because the shortcuts could help us to save a lot of time. We can open the editor from:
Window/settings preferences/hotkey editor
In the hotkey editor first that we have to do is to create an action. So we press new, and then, we have to fill the boxes on the left out. In name we can type AddInbtween1 for example. In description we can type whatever we want that describes our action to help us to know what is it in the future. In the category field we have to select one of the categories on the left to keep the library clear. I add my commands on uses category. And then, in the command field we cut and copy the script code. Then if we press accept the action will be added in our library (on the category we selected before).
If we press list all we will open a window with all the hotkeys listed. This is usefull to know which are the keys that could be usefull and which ones we consider that we can crush with our owns.
There is another way to know what have any key assigned. In the Hotkey editor in the assign new hotkey section. You could write a key an then press query or find. The program will show you what do this key.
And the last step is to assign the action to the key. To do that we have to select the action we just created before, browsing the categories if it's needed. In the assign new hotkey section, we have to choose the key we want and the modifiers (as ctrl or alt) if we want to. And then, press assign. It will ask us if we want to assign an already assigned key press accept and thats all (We can restore defaults whenever we want so don't worry).
I hope this helps and is clear.
