Extras

There are some extra settings for the geckolib model you can change
You can click on the "Extras" button it the CNPC model settings GUI

And you will see the GUI with extra settings for your geckolib model
Let's look a bit closer on all of the settings available here

Head Bone Name

Sometimes you want your mob to have a head, which is rotating separately from the body (like in regular CNPC).
Your model consists of bones, grouping cubes and other bones. So you can select the name of the bone, which is supposed to be the head of the model, and it will rotate as a head.

Transition Length

Usually you want your animations to smoothly transition from one to another and Geckolib provides this feature. When a new animation is activated, the model will smoothly transition from the previous state to the beginning state of the new animation. And here you can select the number of ticks it will take the model to move from one animation to another. The more ticks you set, the longer it will take the model to change the animation, the more smooth transition will be.

Hitbox settings

Every entity has its own hitbox. It is the area in which you can hit the mob, and also the area which will trigger the rendering of an entity if visible. By default, geckolib modeled npcs have a hitbox which is 0.7 blocks wide and 2.0 block tall. But for some of your models you want hitboxes of very special sizes. You can select the width and the height of your hitbox in blocks and perfectly tweak the hitbox size.

Hurt tint

In minecraft when you hit a mob, it turns red for a half of a second. Usually you don't want this for your nice looking geckolib models. But sometimes you might want to save the vanilla-style hurt tint. You can select whether you want the model to use hurt tint or not by clicking on the "Enable Hurt Tint" button.