[Evolution] Secret HTML editor !

[<sdisemi tin it>]

Dear All,

I am using Evolution 3.18.5.2 on Mint.

It has been a source 
of considerable frustration for me that Evolution client composes HTML, 
but there is no way to view and edit directly the html source code, 
especially on those occasions where the code "goes to S**t" as they 
say.
The other day I was banging away blindly in the message 
composition pane and I  held down the control key rather than caps lock 
whilst typing.
I raised my eyes to the screen after a few seconds and, 
lo and behold,  an html editor had miraculously appeared !!!

Rather 
than my having to tediously repeat 26 combinations of <control> a, b, c 
etc, can somebody "in the know" let me know what the "secret" keyboard 
shortcut is for opening the html editor ?

And, whilst they are at it, 
why not let us long-suffering users of this "complex" piece of software 
have a complete list of all the other "hidden" keyboard shortcuts which 
have other hidden functionalities ?

Sincerely,

Stiphen