You know when you have a mix close and you want to try something new.  It would be cool if you could hit a freeze button to save current mix, make changes and then A/B  the new and the old.  Currently I do a save project  and then a reload but A/B 'ing is hard.  Just a thought.

I know what you mean , yet there is an easy way around it 
you can have multiple projects open in SONAR …I do it all the time … there is nothing to reload ..
when you hit minimize , you can see all the open projects over by the lower end of the task bar …you can always maximize the project you want to edit ...
 
what about doing something along these lines ...
get your mix to where your as close as you think you can get before you want to experiment ...
on that mix do a save as and call it by its song name and add mix 1 to the title ….
while leaving that song / mix1 project open ,  reopen the original project …be bold , take chances , edit it to your hearts content …then all you have to do is minimize the project and pull up the other one …mix 1 and compare 
if you did something you really dug call it by it's name and add mix2 when you do a save as ...
it is really that simple and there in no load or reload time involved 
hope that helps you in the mean time , 
 
Kenny

Likewise, I save mixes under separate file names to make them easily accessible.

The X4 screen shot that leaked out a few weeks ago has a new "Mix Recall" module in the control bar. So I reckon this is already in the pipeline.

i would just select all, bounce to track, set that tracks output direct to soundcard, and use exclusive solo.