Issues/workarounds
One frame layout jump
When creating widgets, try to use “Desired” size option. It’s in the menu in top right side of the designer, next to Screen Size.
This lets you see how much space the widget itself “desires”, which is sort of like its default layout. If the widget looks weird in its desired size, this can cause a visible relayout. It’s only visible for one frame (Possibly a bug? At least in 4.26), but it can be noticeable.
Text layout jump
If you use auto wrap text, this can also cause a one frame jump when a widget is first being rendered. Using a manually defined wrap point at a certain pixel width appears to fix the problem.