when im mixing on the mixer-view on a plugin window,i loose my computer-keybord,i have to click aside the plugin to be able to use my short-cut keybord.
Besides that, there is an option in the settings that the Spacebar will play/stop if the main window is in the background (press Y to open the settings and then look under General > Playback).
You can make shortcuts a Global Shortcut in the Keyboard/Menu settings inside the program settings if you enable the checkbox there. This might be what you need.