Make "Sites" in Office Save As show all available SharePoint sites
When saving as in Office desktop apps (Excel etc.) you can link to a SharePoint team site. However, if you are a member of multiple sites there is no user-friendly way to navigate all of these sites through this link. For SharePoint installations with multiple sites this is clunky, you have to find the URL of the site you want and insert it in the address bar.
The functionality should be that when you click Save As -> "Sites - [company name]" it should show you a list of all available sites, then you can navigate to the sub-site/library of your choice.
Paul Trower commented
This is something we desperately need - this is a huge gap in functionality.
Regularly people start creating a document in Word, for example, and then have no easy way to navigate to the SharePoint online site collection document library where they would like to save the document.
At the moment people are reverting to saving this to their desktop and then navigating to their site and uploading from there - which is a horrendous experience.
This is causing real problems with regard to adoption and engagement of SharePoint Online Team Sites within our company.