This New term button in the New term dialogue box is really great. And unique.
Facilitates the addition of related term pairs tremendously:
I would like to propose adding the "New term" button to the windows that opens when clicking on an existing term in glossary panes too. This feature would be helpful when adding, for instance, plurals to an existing singular form term.
It's already there. Click at an existing term in the glossary pane and change its form (to plural) in the Term Editor. Then, click the Clone button.