Any better way to move app library path to external drive than using symbolic link?
OK, finally I solved this problem. My solution:


Use Disk Utility.app to create a new blank image with sparseimage type and save it at the external ssd drive.
Then mount the sparse image at the target location, such as hdiutil attach /Volumes/&lt;externalssd&gt;/file.sparseimage -mountpoint ~/Library/Containers/&lt;target_path&gt;
move all the original files to the mounted point. 


That's all. By the way, you need to quit the app first and rename the target directory to something else before mounting the image obviously. 

One more tip: you should make sure the target directory you want to move will not have any broken symbolic links after this workaround by running find . -type l -ls command.