I made some small corrections to the formatting of your last edit of Kdenlive/Manual/Timeline/Editing. I am not sure exactly what you wanted to achieve, though. I gather that you want the tags to be displayed verbatim - the accepted way to do that is the <nowiki> tag. The <keycap> tag is for key presses, and it may confuse translators if you use it for other things and it will give strange results when the wiki-manual is converted to a help file (docbook format).
Did you want the grey background as well? (I am not sure that can be converted into docbook format.)