You can activate the following functions for all the E-Mails in an E-Mail thread at once:
forwarding E-Mails
moving or copying E-Mails to another folder
marking E-Mails as read or unread
categorizing E-Mails with a label
deleting E-Mails
How to activate a function for all the E-Mails in an E-Mail thread at once:
Select the current E-Mail in the E-Mail thread in the sidebar. The current E-Mail is listed on top of the E-Mail thread.
Click on Entire thread on top of the E-Mail in the display area. Select a menu entry.