Add 50% option to "Stack on Mobile"

[bradhogan]

What problem does this address?

Currently, you can only choose to either keep ALL columns or stack them.

What is your proposed solution?

It would be very useful for designers to have the option to stack columns with a max column width of 50%. If the "Stack on mobile" is toggled "on" maybe an option to show "mobile column width" with the same options as normal column widths (with just % as an option)?

[annezazu]

@bradley2083 thanks for opening this issue! From my vantage point, this directly overlaps with a few different current issues including #41781 Mind commenting there and closing this out to prevent the convo from being too spread out?