A group turns several layers into one. Select it and the gizmo, the Transform rows and the keys act on the whole thing. Move, rotate or scale the group and everything inside follows. Each layer inside keeps its own animation. That is the trick this page teaches: wheels that spin on their own, inside a car that slides.
Add a Box and two Cylinders from Shapes. Place them as a car: the Box is the body, the Cylinders are the wheels.
Shift-click one wheel, then the other. Turn Rec on. Whatever you change now becomes a key.
Scrub to 4 s. Wheel-scroll the Rotation Z field up to 1440. Both wheels take a key. A key at 0 s is added for you, so there is something to spin from.
Right-click a wheel key and choose Easing: Linear. The wheels now turn at one speed instead of easing in and out.
Shift-click the body, so all three are selected. Press ⌘G. Type Car and press Enter. Nothing moves on the canvas. In Layers, a Car row appears with a triangle, and the three layers indent beneath it.
Scrub to 0 s. Rec is still on. Drag the car a little to the left. Car takes a position key.
Scrub to 4 s. Drag the car across the frame. A second key lands, and the Car row in the timeline now holds a clip from 0 to 4 s.
Turn Rec off and press Play. The car slides. The wheels spin the whole way. Two animations, one object.
Select Car and wheel-scroll the group's Scale. Everything grows together, from the ground up, spin intact.
Position, rotation and scale. Lock, hide and Solid also pass down to every layer inside.
The group's keys and each layer's keys both play. Rec with the group selected keys the group. Rec while you are inside keys the layer.
Double-click a part to step inside. The rest of the scene dims and a breadcrumb shows where you are. Edit like normal. Esc steps back out. Nothing gets ungrouped.
Drag a layer out of the group in Layers to free just that one. Or select the group and Ungroup with ⇧⌘G. Every layer stays where it is. If the group had keys, its animation is removed. Undo brings it back.
Any layer type: text, SVG, PNG, 3D, city pieces, other groups. The Camera cannot be grouped.
Both take the whole group, layers and keys included. Undo restores it all.