Fix size of panes

I am new to atom and use it for coding (haskell) and writing(markdown). I like it but have a difficulty to find a way to avoid the regular resize of panes. I use a dual screen situation and want to avoid panes crossing the
division in screens. on the right screen I might keep the terminal window at a fixed size, independent of what other panes are open.
Therefore the question: is there somewhere a button (command) which allows to fix the size of a pane (or the split) so it is not dynamically adapted?
I am not asking for removing the dynamic adaption, just to allow it switched of for some panes.
Thank you for a solid foundation for working!