Cross for the numbers
Cross mark for cells
Спасибо за прекрасный ЯК от "тоже довольно храброй львицы из китайского календаря"!
To activate block mode, press and hold down CTRLand move the mouse while pressing the left or right button. You will see a frame with translucent filling. As soon as you release the mouse button, all the cells that have been highlighted will be colored as selected, or marked with crosses if you right-clicked them initially.