Great tip!
Personally, I hand curate my collection with the help of MediaElch as it has a button to force a rescan once I've done my updates.
Incidentally, what skin are you using?
Have you tried MediaElch?
I've used it bit for NFO files and seems to do the job. But I haven't used any others, so I have no comparison. I think it may be able to edit Kodi's SQL tables (it did for XBMC) but don't hold me to that. :)
Can't you create NFO files with XML data (i.e. no URL)? http://kodi.wiki/view/NFO_files/TV_shows#Video_.nfo_Files_containing_XML_data
~~There's also programs to create NFO files for XBMC. E.g. http://www.kvibes.de/en/mediaelch/~~ Seems to require you to import XBMC's database. At least I can't seem to do anything.
Here's something more along the lines I was thinking: Basic NFO Creator
I've been using MediaElch (company and site are German, but the app itself is in English)
http://www.kvibes.de/en/mediaelch/
It is not perfect, but pretty well featured and gets the job done. I manage my >500 movie collection pretty seamlessly so my XBMC doesn't have to do any scraping work. I periodically look for others and there are very slim pickings. I am interested to see if others can offer other suggestions.
Hope this helps!
EDIT: (Sorry, hit Save too soon) I like this program because it has several lookup resources (TVDB, IMDB, Fanart.tv, etc) but both when/which it uses, as well as how much data it does or does not populate, is entirely under manual control. You can easily create/edit NFO files without doing any automatic server population at all, just setting the data you want.
I have done this exact thing with all my Christmas specials. I have a "show" called Christmas Specials and then name everything S01EXX.Showname. I like to keep each show in a separate folder so for me it's \Television Shows\Christmas Specials\Season 1\Showname\S01EXX.Showname.ext but I don't think they have to be in separate folders. I then use MediaElch to create the nfo files manually. Usually I just clean up the display name and add a blurb about the show if I can find one quickly to copy/paste. It works perfectly and then I set that particular show to display in alphabetical order instead of episode order and the result is an easy to find list of all my Christmas specials.
Why not use MediaElch?
http://www.kvibes.de/en/mediaelch/
It has been around for more than a couple year, it scraps the data so that you don't have to have your HTPC on the internet for Kodi to ad it to its library. Also has a great renaming feature, for Movies and TV Shows
Use local .nfo files to control what season the extras are grouped with. For example, to show a pilot episode as the first episode in season 1 add the following to the .nfo file for the extra:
<displayseason>1</displayseason>
<displayepisode>1</displayepisode>
Change the numbers accordingly and the extra will be added where you want it. There will still be a folder with all the extras as well but this way they are also displayed in the order you want.
I use MediaElch to create my .nfo files. It allows you to input the displayseason and displayepisode when scraping.
For the Mac:
MediaElch (I use this daily) - Free, and works with Movies, TV, Concerts, etc. http://www.kvibes.de/en/mediaelch/
iDentify2 - http://identify2.arrmihardies.com
Once you've got everything sorted, you can stop dicking around with the scraping functions and just set it to use local info only and your shows won't get rescraped with bad info.