A little known feature of Adobe Illustrator is that you can input mathematical expressions into number fields and it will evaluate inline. It allows for the +, -, /, and * operators. For example, if I have an object at x position 45, I can change the value to the following:
45 * 2
When I press tab or enter, the value will be calculated to 90. That is a simple example, but imagine you have a position with an ungodly number of decimal points. This technique will allow you to quickly, precisely, and consistently translate/rotate by a specific value. You no longer need to be good at mental math or use a calculator.
I think this would be a great addition to Spine. I don't think it would be incredibly difficult to implement. It would just require a few more string evaluations when users traverse number text fields. You don't have to support more than 2 terms in an expression to make it useful. Thanks for your consideration.