Q: I was surprised I couldn't type '+10' into the value field, but no go.

THIS HAS BEEN POSTED TO PETER WATJE'S PLUG-IN LIST.

A: There is a simple way to change ONE field RELATIVELY to its current value. The only field it doesn't work is the time/value field of TrackView. To change Keyframe values or times, you should first RIGHT-CLICK the Key to display its floating window. There you can enter

r100

if you want to add 100 to the current value. Use r-100 to decrease the value.

This method works in any MAX value field.