Flex with stretch along the cross axis

Description

Combining flex with stretch along the cross axis seems missing or non obvious.

What MCU/Processor/Board and compiler are you using?

Emulator

What LVGL version are you using?

8.1

What do you want to achieve?

I am trying to convert an existing 7.11 layout to the new API and flex layout. In several places it would be very useful to be able to stretch an object along the cross axis to fill the available space, i.e. align-items: stretch in CSS parlance. However, this option seems to be missing or is at least not obvious to me.