Would it be possible to instruct dictionary to consider names of the Charaters using the Character template as correct in the dictionary?
I mean: Identify names, surnames (single and double), and nicknames, and not highlight them as errors.
That would help to not find some many words with a red line under, and also to identify when I am not writing the character name properly.
Thanks.
This would be very difficult to actually accomplish since there really is no such thing as a character sheet in Scrivener. In some of the project templates, there are document templates which have been called as such, and contain forms which can be filled out as such, but this is not a formal system and is completely customisable. It could just as easily be potted plants instead of characters—trying to guess that information would be the stuff of a flawless spam filter. 
Now, what I could have sworn I remembered seeing at some point was the project auto-complete list (which is a great place to store character names anyway) being ignored by the spell checker, but I might just have been dreaming about that or something. I can’t find any options for enabling that functionality, and it may not even be possible since the spell checker is an Apple thing, and its custom dictionary is system wide, not per application, and certainly not per document/project.
At any rate, it’s pretty easy to right click on “Mr. Stengel” and inform the spell checker to ignore it in the future. You only have to do it once and it will be good in every application on the Mac.