Accidentally, I've somehow entered the "drag to pan" mode – I was able to drag the "canvas" to move around instead of needing to scroll. The mouse cursor was the "hand" type instead of the pointer one that selects things.
This mode would be very useful to me as scrolling doesn't work well on my laptop (https://forums.balsamiq.com/t/scrolling-doesnt-work-on-my-touchpad/3939/5) but I can't figure out how to enter it deliberately. Any tips?
Oh totally, @borekb. You can drag and pan if you hold space while you drag. I'm sorry that I didn't think to tell you about that before.
Here are all the keyboard shortcuts, for quick reference.
Cool, I was trying all the standard modifiers like Alt, Shift or Ctrl, didn't think about space. Thanks.