Command+arrow for moving the cursor while editing text (rather than selecting shapes)

I often edit big blocks of text in OmniGraffle, and my hands are programmed to use cmd+left arrow to move the cursor to the beginning of the line and cmd+right arrow to move the cursor to the beginning of the line.

But in OmniGraffle, these keyboard shortcuts select different objects (which is very useful too).

My question: is there a way to get back the system cmd-arrow functionality while editing text in OmniGraffle?