To select a few tasks on the board, simply click on them while pressing the CTRL key.
Alternatively, you can select cards by drawing an area rectangle on the board with the mouse pointer, just like in your operating system. Once you have your set of cards chosen, you can edit them at once, move them all to a specific column, or another board.
To update all of the selected cards, right-click any of them and use the “Edit # tasks” option in the context menu.
To add or remove individual tasks to and from the selection, keep the CTRL key pressed and click on cards.
To include another area with the existing selection, keep the SHIFT key pressed and draw another area. This way, your previously selected tasks won’t get un-selected.
Furthermore, by selecting a few tasks and dragging them with the SHIFT key pressed, you will duplicate all those tasks at once.
If you need to edit a multitude of tasks at the same time, consider using the import functionality. For as long as you provide IDs of tasks already present on the board, the imported information will overwrite their current data.