Include a library of objects & actions to pre-populate scenes
One thing that "explainer animation" tools often have is a lot of pre-populated settings / objects for characters (and sometimes animations for those objects). For instance, you can drag and drop a "cell phone" to a character, and it will have them hold it, and you can drag in an animation of them tapping the screen.
Other 2D animation tools have things like walk/run cycles, jumps and hops, dancing, etc, that can drive the animation of a character at a certain point.
Not only would it be great to have a library of tools to create rich movements (and add objects, bg furniture, etc), but it would be great if custom variants could be posted on a public forum to share with other users.
Right now this is probably limited by the fact that a scene is essentially just a single "puppet", which is hugely limiting. Ideally a scene should contain multiple puppets, objects, and cameras. But once that happens, being able to quickly build actions with pre-programmed objects / actions would be AMAZING for quickly creating 2D character animations.

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Anonymous commented
One sub-category that would be hugely useful would be facial actions, which may include movement of eyes and eyebrows, mouth position, and head tilt in a single "expression" (such as extreme disgust). That's a lot of work to do by hand.