How to add a padding to Preferences dialog?

When I was experimenting with tweaking the “Welcome to Gramps:” gramplet, there was a kind instruction on how to add padding to the left & right sides of the content in the Dashboard gramplet. (Illustrated in the stacked undocked dialogs shown below left.) It gave a much cleaner appearance.

I was wondering if there was a similar suggestion for padding to be universally applied in each of the boxed Configuration options in the Dashboard Configure dialog?

Adding a couple pixels inside the outline at the top, left and bottom of the box would make the dialog cleaner. (The right edge oddly has a fairly wide margin.) The box not being horizontally centered seems odd too.

Where can the padding be tweaked for these dialogs?

I've been looking through all the existing Gramplets configurations and cannot find an example of a checkbox. But there doesn't seem to be any. (Maybe I should be using a tool for laying out these GUI elements instead of doing it all in the Notepad++ text editor?)