You can access the context menu ☰ in Folder tree. It offers a list of actions to facilitate your work with emails.
To open the context menu, click ☰ or right-click a folder in Folder tree.
Figure. Context menu.
In the context menu of the account, you can:
Add Folder
Create a new Search Folder
Add Shared Account
Share Folder
In the context menu of a folder, you can:
Manage all items (in Mail): mark email as read, copy or move to folder, empty folder- Add Folder: click to create a subfolder
Rename Folder: type a new name and press Enter.
Move Folder: click and select a new folder, the present folder will become its subfolder
Add to Favorites: click to add a folder to the list of favorite items 
for quick access
More Options: click to select either to export or to synchronize a folder- Share Folder: click and enter the email address of the account you want to share the folder with
Delete Folder: click to permanently delete the folder