NO Javascript/jQuery/PHP or any other script language. JUST CSS.
FINALLY!! a simple method of having a slide up/down and cover/uncover without hacks or max-height.
I have recently been investigating the grid styles and came across the fact that the style 'grid-template-rows' can be transitioned. This led to the seeing that it is possible to transition from 'grid-template-rows:0fr;' (equivalent of height:0;) to 'grid-template-rows:1fr;' (equivalent of height:auto;).
With a little trial and error I also found that using 'align-self:end;' it is possible to anchor the information to the top of the grid box to give a slide up/down effect.
So I think that this fixes all the problems that we have had over the last few years trying to transition from 'height:0;' to 'height:auto;'.
All done with a couple of styles.