In fiddling around working out how to use Scrivener, I seem to have done something that stops the Special Characters menu from appearing when I go to Edit > Special Characters 
Any tips on how to restore it?
Have you tried just hitting Control-Command-Space?
Which version of OSX are you using, and which version of Scrivener? I’m using 10.10.4 and Scrivener 2.6. I don’t have an <Edit » Special Characters> menu, I have <Edit » Emoji and Symbols> — shortcut Ctrl-Cmd-Space — which brings up the system Character Palette, where you can find whatever character you’re looking for.
Also, using that palette, you can add glyphs to “Favourites”, to make them easier to access, or you can set up a suitable keyboard shortcut to one you use frequently through <System Preferences » Keyboard » Text>
HTH 
Mr X
Thanks for replying, guys - I still don’t know what I was doing wrong, but the problem seems to have resolved itself, so no harm done!
I’m now struggling with a related problem. I need a particular special character that doesn’t appear on the menu, the Anglo-Saxon letter æ with a breve over it, but I don’t know how to type it. Any suggestions? Perhaps some kind person could just type it for me to copy and paste? 
[size=200]æ ǽ ǣ
Æ Ǽ Ǣ[/size]
Press CMD ALT T to bring up OS X Character Viewer. Tons of characters in there. Click the gear icon and choose Customise to add extra palettes.
EDIT: In El Cap, the shortcut is CTRL CMD SPACE. If you only see emojis, tap the CMD icon in the top right-hand corner and the full character palette will open up.
Thanks so much - what I really need, though, is a breve (the u-shaped mark that means a vowel is meant to be pronounced short)
No idea how to achieve this
This?
[size=200]Ӑ ӑ[/size]
You’ll find it in the Cyrillic character palette, or Latin Extended-A. Enable the palettes and then search for breve.
EDIT: In El Cap, the shortcut is CTRL CMD SPACE. If you only see emojis, tap the CMD icon in the top right-hand corner and the full character palette will open up.
[attachment=0]ae.png[/attachment]
That, but over æ rather than a…
Doh! When I am back at a Mac, I will check again for you.
Hunting around, æ with a breve isn’t supported by OS X’s system fonts.
This link explains (and offers a solution)…
Maybe this is just my lack of OS X familiarity talking, but on OS X 10.10.5 with every option selected for the character app, I’m not finding the combination of aesc plus breve.
EDIT: …I can see I sat in the thread for too long researching, as Briar Kit has already explained this. AND provided a possible alternative.
We spend our time doing research for other people. Mad? Determined? Both?
You sure they’re the only options?
I’m sure you can think of more.
Ooo, that’s very interesting indeed… Thank you for being awesome 
A pleasure. And I wish I was.