The shortcut Ctrl+Shift+Tab is to return to the previous workbook if the cursor is in a workbook or will return to the previous toolbar if the cursor is in the toolbar. Please also refer to the shortcut Ctrl+Shift+F6.
Step 1: Click any cell in one worksheet;
Step 2: Press and hold the Ctrl and Shift keys, then press the Tab key from the keyboard. The cursor will return to the previous workbook.