All Xcode code snippets exist as a .plist files in ~/Library/Developer/Xcode/UserData/CodeSnippets/
You can simply copy all code snippets (.codesnippet) into this folder, restart Xcode and you should have all of them ready to use.
Note: Create the folder if it doesn't exist already. It is created by Xcode when user adds his first custom snippet.
I named all completion shortcuts to s.... For example, you can input 'slabel' to create UILabel code snippets.
If you want to add this nice placeholder in rounded blue rect simply put it between <# and #> and it will be transformed in both editor and final snippet.