Thunderbird view sortby unthreaded

Also getting annoyed by always have to go to the menu item
View – Sort By – and then select ‘Unthreaded’?

Just change the default for new folders and views!

Go to:
Settings – General – Config Editor

Search for the following keys and set them to the desired values:
mailnews.default_sort_type (make sure it is set to 18)
mailnews.default_sort_order to 1 (ascending) or 2 (descending)
mailnews.default_view_flags to 0 (unthreaded) or 1 (threaded)

(And if you want to expand all messages by default then add 32 to the previous value, so enter 32 or 33 as default_view_flags.)

here's some off-the-cuff documentation:

Prefs are named as follows; first three apply to Mail and RSS folders, the second three to Newsgroups.
In about:config  (Tools | Options | Advanced | General, Config Editor), you can enter "news._def" to filter out all the prefs but these.

  byNone        17         byPriority    23      byLocation    29 
  byDate        18 *       byStatus      24  	 byTags        30 
  bySubject     19 *       bySize        25  	 byJunkStatus  31 
  byAuthor      20 *       byFlagged     26 	 byAttachments 32 
  byId          21 **      byUnread      27 	 byAccount     33 
  byThread      22         byRecipient   28 	 byCustom      34 
    * = commonly desired values
   ** = by Order Received (?)

  ascending   1
  descending  2

view_flags -- the second group of values can be added to one of the first group to combine effects, with several limitations:
  Unthreaded       0
  Threaded         1
  Grouped         64  [mail only (?)]

  ShowIgnored      8  [news only]
  ShowUnreadOnly  16
  ShowExpanded    32  [doesn't seem to work]
ShowUnreadOnly will check the View|Threads|Unread menu; this will cause only
unread items to be seen, but doesn't force a threaded view.

The source for the values above is: here

That’s all folks.
Have a nice day!