Size of openend message pane

Firefox 52.0.2

In the table, I can very simply change the size of the columns. However, when a message is opened, half of the table height is taken as space for the message pane. I cannot change that except for clicking a button to open it fully.
Please make the size changeable like for a column.

But most of all: let it remember my choice for the next message, I open, regardless of full or custom size.

Thanks for your message.

This issue is being discussed here:

  • Geir