This must be done on an account by account basis. - select table view - the icon just to right of 'quick filter' button above message list pane - select a message folder and apply all desired attributes - View>sort by from menu bar (if not shown, click alt key) - click the icon at right side of column display in message list pane - select the entry near bottom 'Apply current view to...' - highlight 'folder and children' - move mouse left to see account name and move left again to display all account folders. Now CLICK. - a small menu will appear to confirm setting all folders within that account.

I did a simple (okay, crude) video at https://davidkirk.org/SettingDefaultFolderView.mp4

Thanks for posting this, but I can't follow it at all. I don't see "Apply current view to...'" anywhere. I don't understand what the point of clicking on view menu was in your instructions? And I don't display them as table, i display as cards, but I did as you said and made it table view to see if "Apply current view to...'" appeared anywhere but it didn't. Can you try explaining again please?

Oh, hang on I found it! I notice a different icon right of message list but only when in Table View. I see the option to apply view to other folders. That's a step in right direction, BUT... Doesnt this mean it will make all my folders display in Table View? Maybe I can make table view a bit more usable by sorting columns etc, if I must, but I'd really like to use Card View for all folders, as well as unthreading all conversations (I like every email to be listed, not threaded conversations), and sorted by data descending. Is that possible with Card View? thanks

I specified table view to ensure you had the icon available. Otherwise, use card view or table view as you desire, as that applies only to how the messages are listed, not to the individual folder organization.

So does this mean I have to select Table View to get the icon so that I can apply the organization settings to other folders, then I can switch back to Card view and that will stick across all folders?

Table view and Card view are irrespective of folders. That is a universal setting for how the data is presented, now how it is sorted.

Sorted, took a long while to apply to all selected folders. thanks