"Add new captions segment" button should only create a segment as big as default size or up to the next caption, whichever is smaller

I find I often have to add in captions because the Transcript missed dialogue or sounds that I need to add in. If I press the “Add new captions segment” + button in the Captions pane, sometimes it’s greyed out because there’s not enough space to add one before the next caption, and other times the one it creates will absorb the next caption to create one big caption, delete the text that was in that next one, and replace it with default text (this is very frustrating and I can’t see a time when this is useful).

My feature request is: If there’s not enough room to put a default sized caption in the track before overriding the next one, just shrink the new caption to fill the space rather than absorbing the next one or greying out the button.