Running 8.0.9
I have a simple view with an image on it. I bound the boxShadow style property to some tags to highlight the image if necessary. In the Designer the value of the boxShadow was blank. I clicked the style editor icon to bring up the menu and clicked cancel. The boxShadow property disapeared (along with my binding code). Luckily I noticed and didn’t save it. Putting any value into the boxShadow property prevents it from being deleted. Just wanted to share…
Here’s the style
boxShadow is bound to a tag, using an expression…
If I open the style editor boxShadow is blank
and if click ‘Cancel’ in style editor…POOF… no more boxShadow 
I don’t think a ‘Cancel’ button should do anything.
If it has to do something it should check to see if there is a binding before deleting a ‘blank’ property.
Oddly enough, if you have the style editor open and click outside the designer windows the style editor closes and preserves the blank property. For now, I’ll be clicking outside the designer instead of clicking cancel.