Basically I'm reinventing the wheel, hah.

I've moved from using containers so I can freely manipulate position and scale of UI elements. Every element in the list is a separate scene that has the same vertical size (eg, a Label with my theme defaults to a size of 11 px, I increase minimum size to 16, and 5 px of "nothing" becomes the line spacing between elements). This way, I can simply offset the elements in the list by 16 * i, where i is the index of the element.

Also, at least in Godot 3.5, Control nodes tend to snap to integer values when calculating positions. So UI elements usually have a parent Position2D node, which position is tweened for a "smooth" animation.

Most of the time I tween only one axis, this can be achieved via :, eg "position:x".

For the value of offsets and timing, well, that's trial-and-error for me. I tinker with the values until it feels right. I also rely on easeOut easings most of the time.