To rearrange sheets under a tab, click on the gray arrow that appears on the right side when you hover over any sheet inside the tab. Click Rearrange, and drag to change the order of the sheets.
Don't forget to click Save Sort when you are done.
To move a sheet under a different tab, click Move Sheet under Rearrange.
Doing so will display a popup where you can choose a specific sheet to move to a specific tab.
The process when rearranging your tabs is the same with rearranging sheets. Click on the arrow that appears on the right side when you hover over any tab. Click Rearrange and drag to change the order of your tabs.
Don't forget to click on Save Sort when you are done.
