Idea Summary
A way to make the column max-height in a modal page set to the same as the modal body and flex if the modal is resized. This would also require adding a maximum number of rows similar to how a page has 12 columns. Something like a maximum of 4/5 regions on top of each other. This means modal pages always look full and content that is dynamic always fits the screen perfectly and doesn't look incomplete.

Use Case
Modal pages that are used for things like chat function, dashboards, etc.. In the simple case where you have a classic report displaying chat bubbles as comments and a text field to converse with the chat, at the start when it is empty the classic report will still stretch vertically to the modal page and as more chat bubbles are added, once the height reaches a max-height (similar to the body of the modal) an overflow is introduced to the region instead of the modal body. This retains the initial format.

Vertical Stretch on Items so it grows based on the modal page's height etc.

This will be really useful for pages in which you never want any overflow on the main body but the regions themselves may require scroll, but each region requires the same height.

Preferred Solution (Optional)
When creating a modal page, have an option like “Fixed Column Height” that can be selected and when you have the option selected any region/item within the body of the modal can have the attribute “Stretch Vertically”. When a region is added and this option is ticked. It always stretches to the height of the modal body, and if it grows larger an overflow on the region appears (NOT THE BODY). This way if you had 3 regions side by side, they would always be the same height. If the modal is resized all of these are recalculated and dynamically adjusted to fit the screen.