After right-clicking the Glossary and choosing to define a new term, the window that comes has no Save button, no Done or Okay button, and the only way to get out of it is pressing the X (close) button, which then prompts the user to save changes to the Glossary.

This is unusual and confusing at first, since the absence of a button to apply changes typically means that changes are set immediately/dynamically (like LXDE and XFCE do), but that's not the case.

And if the window requires the user to save changes, then there should be a Save/Apply button (like those of System Settings) or the window should be able to save changes with Ctrl+S and indicate that the changes were saved (like removing the * in the titlebar), but that's not the case. This is a usability and consistency issue.

I see two possible solutions to this: either make changes be saved automatically (which can lead to unintended mistakes by the user since the dialog does not have Ctrl+Z implemented), or add save functionality.