The text editor in yWriter is fairly basic, and contains few of the features found in word processing software such as MS Word or OpenOffice Writer.
Many people have asked whether it's possible to edit their yWriter scenes with a different editor, and the answer is yes. There are two ways to do this, but first you have to configure Windows so that when you double-click an RTF file in Windows Explorer, it opens in the RTF editor of your choice. (Instructions for doing so are different for just about every version of Windows, so I haven't included them here.)
The first way to edit with an external program is to right-click the scene in your scene list, then click 'Open with external editor'. This will run the RTF file as though you'd double-clicked it, which is why it's important to set up Windows to open them in the editor of your choice.
Now, there is no way I can program yWriter to detect whether an external editor has finished with the rtf file, especially given the huge range of editors on the market, so from this point on YOU are responsible for telling yWriter when you have FINISHED editing the scene.
To do this, when you've closed the external editor you must right-click the scene in the list and click 'Finished using external editor'. This will force yWriter to reload the content from disk and update the word count.
Please don't click 'Finished using external editor' until you have saved your work and closed the external editor. Too early, and yWriter will simply reload the older version of the rtf while the editor program is still saving a new one.
The second way to edit externally is to 'print' a scene list to your browser using Scenes - Reports - Print Scene List. This list will contain titles and hard links for every RTF file, and clicking them will open the file in your system default RTF editor. However, before you click any of them you must close your yWriter project, since yWriter has no way of knowing you've been editing files and cannot reload them.
So, if using external editors is supported, why would anyone use the internal yWriter editor instead of a polished word processor? I'll tell you why: autobackups. The yWriter editor takes a realtime snapshot of your scene every 'N' seconds (user-defined), and stores them in a zip file by date and time. These are permanent backups, never overwritten or deleted.
To my knowledge no other editor or word processor does this, and the day you lose three hours work because your computer rebooted is probably the day you'll start using yWriter's basic editor instead of that word processor with automatic bullets, curly quotes and ... what was that other vital feature again, the one which no author can be without? Sorry, can't remember. (I don't bother spell- or grammar-checking until the final draft. Why waste time polishing stuff you may cut from your finished novel?)
In summary, I added the external editing feature because people kept asking for it. However, in the long term I suggest you get used to the yWriter editor.