Did you know you have the ability to move and resize the Office 365 launcher tiles in Outlook on the web? It works like it does on the Windows 8 or 10 Start page - simply drag the tiles to move them to reposition them. Click the 3 dots to expand the menu and select More to resize.
In addition to resizing the tiles, you unpin apps from the app launcher and pin or unpin apps on the nav bar. If the Pin to nav bar link is disabled, you’ll need to unpin an app, as you are limited to three apps pinned to the nav bar.
Note that the changes you make won’t display in the launcher used by some of the Office 365 apps (you won't be able to customize the launcher used by those apps) and Office 365 consumer subscribers, including Outlook.com users, won’t have this option.