First time running Dorico 5, luckily I can still do the bracket. Haven’t seen this before.
You haven’t described exactly what the problem is. That the one selected is mostly off screen? You can scroll within that panel to bring it fully into view if it bothers you.
The only way I can get Vertical to work is something I just discovered… You have to enable both the Vertical and the Horizontal displays in order to see all of the Vertical displays. I didn’t try that until now. Horizontal always works. Vertical only works if Horizontal is enabled.
I’ve run into this too, at least I think it’s the same issue – that the one bracket I actually want, vertical with top & bottom hooks to the right, isn’t visible on the panel. I’ve always had to go into Editing brackets and make a copy of it, and after that the image is visible. But the suggestions here may give me a different way.
You may not be aware that this window is scrollable. The easiest way is to use a trackpad or mouse wheel and all items will come into view. When you also opened the Horizontal View, the scroll bar got smaller and functions more dependably than when it is larger.