I believe it would be overwhelmingly beneficial to be able to leave the parameters window open while designing. Further, the ability to live edit/update multiple parameters while building out a part or assembly would be much easier than having to edit multiple features individually. This would be extremely beneficial especially during the sketching phase, as we would also be able to name and track the parameters in a much more viewer-friendly setting, versus trying to remember to set parameters during each/every dimension we add.
Further, allowing the ability to use excel-like formulas, such as "round" or "average" would be fantastic directly in each parameter. I get around this currently by adding a user parameter and then reference back to it. This isn't a huge deal, but is absolutely cumbersome in the event that we cannot have the parameters window open, as again, you may be creating a dimension or reference, recall you need a formulated answer, then either have to leave a random dimension that needs modified post creation, or you have to quit the definition in order to create the parameter to reference.