Pre-populate a text entry box with the contents of a variable?

I experimented more and found a solution right after I posted this!

Here's the technique: 

1. Capture your original definition into a variable (varOriginalDef) with a text entry field on a slide earlier in the project. 

2. On the slide where you want the learner to review and, possibly, edit the definition, start a trigger when the slide timeline begins, setting varRevisedDef equal to varOriginalDef. 

3. On the object itself (the text entry field), set a trigger that sets varRevisedDef equal to typed value when the field loses focus. 

4. Echo both variables out on a new slide to test them. 

I'll work up a demo at some point and attach it for the benefit of others.