How to make a moving widget the same size as its parent?

I want to create a widget that when you press a button, a widget of the same size slides out from the bottom. For example, if a widget placed at 200x300 is expanded, it will be expanded to 400x300, and if it is 200x500, it will be expanded to 400x500.
However, I’m having trouble setting the size of the slide part to be the same size as the parent. If anchor set to Fill, alignment cannot be set, so the animation cannot be played. It would be tedious to animate all the borders, and it would be more tedious to manually change the size of the contents one by one to match the size of the placement.
How can I auto-adjust the size in this case?

I would reccomend to use an overlay for this case.

And setup the fill setup in their children. In the the animation I set the pivot to 1.0 and 1.0 and setup the scale from 0 to 1.



Let me know if that work for you.

This is not what I want to do, but the idea of ​​scaling seems simple so I’ll use this.
Thank you for your answer.