I was hiding a quantity of rests (the ones caused by shifting some piano notes to the other stave with cross-stave beaming) by the “reduce transparency” method, using the opacity control in the colour popup.
It would seem that if you do this for quite a lot of rests or groups of rests, the colour popup slowly lengthens until it’s bigger than the screen vertical height. If you then quit Dorico and restart it, the colour popup will now fit the screen height once again, and you can grab lower right corner to resize to something sensible. If you then go on altering transparency of more rests, the popup is no longer vertically resizeable and reverts to growing again each time it is used, until once more it’s bigger than screen vert height and you can no longer get to the OK/Cancel controls.
This behaviour only shows up if you transparency-hide a large number of rests in succession. The popup is still resizeable horizontally but not vertically.
I imagine this is not meant?
[Mac Pro, OSX 10.10.5, 3 x 23" screens]