Hmm… If you are on OSX the dialog grows in size to fit the content even if it extends past the height of the application or screen.
On Windows the dialog is sized to the height of the content OR the height of the main application window whichever is smaller. Any content that does not fit is clipped inside the dialog (NET - not extensively tested).
I’ve added overflow auto to the main form and then set the height of some elements in the form to an excessive amount and also set a height smaller than the content on the form and it’s showing scroll bars.
The changes I made will only affect the Windows side of things so I also reduced the height of the form to shortest height possible for the OSX side.
BTW When you resize the main application scroll bars appear automatically in various parts of the application.