Is there any possibility to “mark deleted as read”?
Hi,
this can be done by right click on email and select mark as read, or click on email and using shortcut ctrl + q.
with regards
Jan
That’s not what I meant. Can it be applied to ALL deleted messages without clicking each of them?
right click on Trash folder and select mark all as read, or use ctrl + a in trash folder that will select all emails and after this you can use ctrl + q or right click and mark as read again 
I do this several times a day and I hoped it could be done “once and for all”. It’s not so hard to add this button in Settings -> Mail -> Read, is it?
I don’t understand, you want all email that falls into trash be marked as read automatically?
If so then this can be set by rules, that emails from address/es by your choice will be moved to trash and marked as read.
Jan