I was redoing the layouts in an old solution and decided to convert a row of buttons to button bars. I was converting it to the "Wave" theme, which has a nice gradient on the buttons, but I discovered it did not apply this to button bars, they're just flat white. So I selected a button with the gradient appearance that I like, hit the "format painter" (eyedropper) button in the tool bar, clicked on the button bar, and... nothing. I used the format painter to copy the gradient to several other objects on my layout to confirm that it was otherwise working as I expected.
Similarly, using the style copy & paste features in the inspector didn't work. They're available, but didn't do anything when I tried to paste a copied style from a button to a button bar. If I selected "Button Bar: segment" instead of "Button Bar" near the top of the appearance tab of the Inspector, the style copy and paste buttons become grayed out.
It would be nice to be able to copy formatting, like text formatting and gradient backgrounds, to button bars, like you can to virtually any other layout object. Attempting to replicate the Wave theme's button gradient by hand on a button bar that it can't be copied to is slow and difficult to do precisely.
I did see that someone posted about copying styles to button bars last year, but that thread didn't mention the format painter failing so I'm posting this separately.
FileMaker 15v3, running on MacOS Sierra.
Thank you for your post.
Our Development and Testing departments are aware of this limitation. I have attached your post to the original report. When more information becomes available, I will post again.