I have a 3TB Hardisk for my 27 inch iMac. I have added a partition to the current Macintosh HD and divided the storage space to :
1. Macintosh HD - 1 TB - Mac OS Externded (Journaled)
2. New HD - 2 TB - Max OS Extended (Journaled) ( Use as Storage for working files and resources )
The Macintosh HD already have softwares and programmes installed. Reading from other sites, I can partition even there's data on it because it will just dividethe drive into 2. So I use Disk Utility > just click on the add "+" button to divide Macintosh HD to above partition. But the options button is greyed out. After that a message appears " Click to Apply to apply changes. To make more changes you must first apply this change ".
After clicking apply, the partitions have been divided to two but I could not add another partition for New HD.
Is there a maximum partition for the HD? Or does this problem occur because I already have data on the original Macintosh HD?
You have a Fusion Drive as evidenced by the Type: Logical Volume Group in your screenshoot. You can ONLY add 1 additional partition which you have done. Below is from Apple' About Fusion Drive.
Can I add a partition to the hard disk with Fusion Drive?
Using Disk Utility, you can add one partition to the hard disk on Fusion Drive. Once you add the partition, the "plus" symbol in Disk Utility to add additional partitions will be grayed out. You cannot partition the Flash storage.