I think blackmarket controls need to be accessible from the main screen , or have instant keyboard shortcuts to buy and sell crystals and metal in any screen view.

Ive been playing a tough game...3 hard ai vs me on small galaxy, where im pretty much squeezing every penny and trying to get out cobalt ships asap and thus im literally back and forth from the diplomacy screen every 15 seconds to redirect crystals into funds and that is very micro intensive.