Make Web Parts ReUsable
It would be nice to be able to configure a Web Part once, and then reference it on different pages. This would give a central point of management to propagate a change through the many pages that the particular Web Part was used on. This could be very useful for navigation menus (a List Web Part), or "related content" sections (Highlighted Content or News Feed with a Filter).
Katja K commented
Agreed, we have page templates, it should be possible to save a web part as reusable one like it works in WordPress and apply it in any page within a site. Export would also be useful so it can be carried across other sites.
Floridian SP commented
They used to have an export function where you could save a file that was XML. Then import that onto a new page and save a LOT OF TIME configuring web parts. Since web parts like people and quick links can represent hours of work, this is hugely needed.