Creating MOGRT | Shape Anchor Point Stays Fixed When Extending Shape Width

Hi everyone,
I’m hoping someone can help me out. This is a bit tricky to explain, so I’ve attached the After Effects file.

I’m working on a Lower Third MOGRT in After Effects, and it’s almost finished. The only problem I’m stuck with is the anchor point behavior when changing the width of a shape.

I have a shape behind the name that can be extended (x-scale) to the right using a slider in the Essential Graphics panel. Since it’s a bezier shape, I created null controllers for the path points. To scale the shape, I linked the position of these path-point nulls to a slider control. I had to do it this way because all corners except one are rounded, and I wanted to keep the amount of roundness when scaling.

The anchor point of this shape should always stay in the top-right corner (the corner at 90 degrees). This is important because the shape has a pop-open animation, like a speech bubble, that scales from that corner.

What’s happening

• At the minimum width, everything works correctly: the bubble pops open from the top-right corner.
• When I extend the shape to the right using the slider, the anchor point does not move.
• As a result, the pop-open animation no longer comes from the corner of the shape, but from a point further to the left.

What I already tried

• Create a new null
• The pop-up scale animation is keyframed on the null.
• The shape is parented to the null.
• The null’s position is linked to the same slider that controls the shape’s width, so the null should always stay at the top-right corner.

The problem with this approach is that when I use the slider to extend the shape, the entire shape moves to the right, because it’s parented to the null for the pop-up animation.

I’ve been trying to solve this all morning and can’t find a solution. Any help or ideas would be hugely appreciated. Thank you!