Preferences > Interface > Toggle single hotkeys

Switches between allowing single key hotkeys (hotkeys without modifiers), and allowing typing directly to the prompt line.

AliasStudio allows you to select two different behaviors when begin typing while using a tool:

Prompt line mode: any typing goes directly to the prompt line. You can only use hotkeys that have a modifier key (Alt, Shift, Ctrl).
Single key hotkeys mode: any key presses are interpreted as hotkeys first. To type in the prompt line, you have to click it first. Single key hotkey mode allows you to work more efficiently by assigning tools and menu items to single key presses.

Use this menu item to switch between the two modes.