Paste Special >> Overwrite selected glyphs does not work in 1.3.20. It pastes nothing. This comes up in the console:
4/30/13 9:29:27.421 AM Glyphs: *** Collection <__NSArrayM: 0x1084a2ed0> was mutated while being enumerated.
4/30/13 9:29:27.431 AM Glyphs: (
0 CoreFoundation 0x00007fff98ecdf56 __exceptionPreprocess + 198
1 libobjc.A.dylib 0x00007fff9442dd5e objc_exception_throw + 43
2 CoreFoundation 0x00007fff98f57ecc __NSFastEnumerationMutationHandler + 172
3 Glyphs 0x00000001000451e1 Glyphs + 283105
)
I cannot reproduce this in 1.3.20.
Which OS version are you running?
EDIT: And does this still happen after restarting the app?
On 26 Apr 2013, I reported to support@ that it was still happening with 1.3.19 (487) for bug 213 (since I couldn’t reopen the bug). I also tested, again, with 1.3.20 and still see the issue.
OS X 10.8.2.
Still happens after restarting the app. I think I recall even trying a full reboot, at one point.
What exactly are you trying to paste when this happens? Glyphs with paths and components or just paths?
In my case, I’m trying the simple case of copying and pasting a single glyph. Eventually, I have a number of glyphs that I want to copy over to replace some designs (while maintaining the history of layers in the glyphs being copied).
2 masters: 1 has paths only; the other is empty.
No components.
Using the same option that DTF mentioned:
Paste Special >> Overwrite selected glyphs
So Glyphs has a ‘Paste special’ command, you say? 
On Lion it’s nowhere to be seen – it shows up in the ‘Edit’ menu only if I search for it by typing ‘paste special’ in the Help’s search field. I run the latest 1.3.20 beta, of course…
Two ways to get to Paste Special:
- Press the Option key while viewing the Edit menu.
- Press Option-Command-V in the Font view.
fyi.
Thanks for the test case. I could fix it.
I didn't know this trick, thanks, but still: why isn't 'Paste special' displayed there in the menu by default?
Yes, once you know the 'Paste special' option exists.
This is a standard feature of MacOSX. You can have alternate menu items to group similar functionality. Most system apps (Safari, Mail …) use it, too.
OK, this might sound a bit contentious – can’t avoid it sometimes, sorry – but hiding functionality from the user “because Apple does it, too” is not the valid reasoning I was hoping to hear to my question about why isn’t ‘Paste special’ displayed there in the Edit menu by default… not that you owe me an explanation, anyway. But consider this: despite being a power-user of Macs at home and at work for almost ten years now, I did not know about this user-unfriendly hidden-menu-thing, and I bet lots/most of pro Mac users are in the same position… If you don’t have a sensible, logical reason why things should remain like this, maybe you guys should reconsider.
It gives the option to have more functionality without cluttering the menu.
Version 1.3.20 (489) OS X 10.8.3
I didn’t know this command existed so tried it; it works as I would expect it to whether copying from one cell to another in a font or between two fonts.
I’m glad to know about the command because it copies widths also.
Only users who know the secret "handshake" will have access to "more functionality" -- that's the problem. For the others the program will actually be more limited, not more functional.
Is solving a small problem - lengthy menus - worth it while creating a bigger one - effectively missing options? (I’ve seen the other hidden entries now).
These are not all the arguments I can come up with, but I’ll stop the pestering here, and start a different thread with a different question. Thanks 
Perhaps in the upcoming revised documentation ALL of the commands can be listed in a table?
Rest assured, all of this is covered in the handbook.
Yes George Thomas, that would be nice! I did love and used the paste special function in FL a lot. I would love to see it more elaborated in Glyphs!