You can select as many flow elements as you like at the same time, except that
a connection and other flow elements cannot be selected at the same time.
To select multiple flow elements
at the same time, do one of the following:
Drag a selection rectangle around the
flow elements in the canvas.
Click on a first flow element, and then expand the selection by
clicking on other flow elements while holding the Ctrl
key (on Windows) or Command key (on Mac OS).