> 1) What does the +swf mean?
The flash module was detected and successfullt loaded (this 
adds basic flash files parsing)

> 2) My single project now has a number of URLs listed in 
the 
> Web Addresses section.  When I wish to perform an update 
> action, how do I turn off those sites for which I do not 
> wish to have the update action performed?
You can't update only certain URLs and not other ones -- 
youhave to update the complete project (because of 
interactions between different URLs and naming/linking 
problems)

> 3) If I have to split my one project into several 
projects 
> for the purpose of selective updating, a) how do I 
> accomplish that so that an update action will not cause 
the 
> new project (with some of the old URLs) to be completely 
> downloaded anew

Copy the project folder (INCLUDING all files, and cache), 
run winhttrack and select the copied project, delete 
unneccessary URLs, and select "Update"

> , and b) how do I preserve the mirrored 
> cross-links between the new projects?
This isn't possible, unfortunately

> 4) Also, what significance is there to listing a URL with 
> and without a preceeding plus (+) sign?  Or is that 
filter 
> designator obsolete for WinHTTrack?
The '+' sign is ONLY used for filters, NOT links.