KDEPIM 17.12: pane that show message structure missing?

[Martin Steigerwald <martin@lichtvoll.de>]

Hello.

With KDEPIM prior 17.12 I always had a pane that shows the message 
structure where I could select which part of the message to view in the 
message content display area. So with messages that are both available 
as text and HTML I could select which one to view.

This is gone since KDEPIM 17.12 and I found no way to enable it again. I 
remember there was an option but I digged through all menus and 
configuration options three times without finding it.

Any idea?

Thanks,
-- 
Martin