You have several tabs open, and the cursor/focus is somewhere within the "Find" toolbar that appears at the bottom of the screen (shortcut = Cmd+F).
Steps to reproduce:
1. Open a file in the studio editor.
2. Open the find toolbar (CMD+F).
3. With focus in the toolbar press CMD+tab.
User should be able to use OS keyboard shortcuts while in Studio.
Keyboard shortcuts do no work while focus is on the find toolbar.
This also happens for the Open Resource shortcut (CMD+T) and the Close Window shortcut (CMD+W).