When you copy-paste blocks from a file to another, there is a chance you get the “Block name conflict” warning.
The only option is to move forward with the copying, with various options as to how to deal with the conflicts.
But what if you simply want to abort and fix the names in your own sweet way ? Well, you just can’t.
You might as well hope you’ve saved the file recently and reboot the computer.
So how about adding a “Cancel” button ?
but I think the Cancel button should be a little bigger. And the font too! 
// Rolf
Hi Oliver, what happens if you chose the first option Keep current block? as I understand this should be the equivalent to cancel. Not in front of Rhino now.
Hi José,
No, it’s not equivalent.
If you choose “Keep block” (which in itself is not very clear), the blocks will be imported with their transform, but with the definition that was already in the file.
Cancel would just do… nothing, and that’s generally what I want to do when I have a block name conflict because it means that I’ve got something wrong in my naming scheme, and I certainly don’t want Rhino to do something in batch about it ; I rather analyse the situation and fix it myself.
The risk here is to screw up the block structure completely.
Yeah, I just tried it, and even closing the dialog box hitting the x will proceed and paste the block. So yes, It makes a lot of sense to add a cancel button to that panel.
José