The editor

The inspector, and pose-then-key

There's no record mode: move the playhead, change a value, and a keyframe appears at the playhead. Posing and keyframing are the same gesture.

Every field scrubs: Drag a value’s label to change it. ⇧ is coarse, ⌥ is fine, and the whole drag is one undo, not one per pixel.
Properties are grouped as CSS groups them: Transform, opacity, filter. Members of a group share one declaration, which is why their order matters and why they animate together.
Values outside the slider are allowed: The ranges are soft. Type 720 into rotate and it takes it; the slider is only there for convenience.
Keyframe fields: Selecting a diamond opens that keyframe here: its time and its value. Its curve is named here too, but edited in the curve panel beside the timeline, so there’s only one editor for it. Click the curve row to go there.
Transform origin and perspective: Settings, not tracks. An origin that moves during a rotation sends the element along a path nobody drew, and without perspective a 3D rotation is an affine squash instead of a turn.
Border width and shadow color: The other two settings, for the same reason: without them, the animation is invisible. A border color paints nothing on an element whose border is zero pixels wide, and without a color setting a drop shadow would always be black. Leave the width blank to keep whatever your own CSS says. Blank isn’t zero: zero removes a border your component drew itself. The shadow’s color is a setting because its strength is the track, one number that drives its offset and blur.
Viewport width, at the widths that matter: A per-element setting, not an animation. The chips (auto, 375, 768, 1024, 1280) are a phone width and Tailwind’s md, lg and xl breakpoints, the widths your markup’s md: and lg: classes were written against, so they’re where its layout actually changes. Check an entrance at a phone width and a desktop one. Auto is content-sized, and it’s the default.
Sections fold: Presets, properties, color, states, transform and the motion path each fold, and stay folded or open next time, so you can collapse what you’re not using. Select a diamond and the keyframe section opens on it, with its time, value and curve.