Hi there,
so, i had a nose around, and i found this open issue relating to moving metaboxes in the block editor:
https://github.com/WordPress/gutenberg/issues/5821
The issue is still open, so it doesn’t look like there is a core way to do it ( that isn’t a bit of hack ).
But that issue did link me to this ACF issue raised by Elliot:
https://github.com/AdvancedCustomFields/acf/issues/114
Which kinda reads like they may have a method of doing what you require.
Might be worth asking ACF support if it is possible.