Objective
ver2.3.0
All adjustments made in the 2D window automatically synchronizes with the 3D window. Simulation automatically ends when making a modification on 2D Pattern while simulating.
ver2.2.0
Once the sync button is activating, any adjustments, not only design adjustments, but also sewing lines, print textures, particle distances get reflected in the 3D window. Even if the synchronization is off, activating the 
Simulation tool auto-activates the 
Sync tool and reflects on the 3D window.
Location
Main Menu ▶ Sync (Ctrl + D)
2D Toolbar ▶ Sync (Ctrl + D)
Operation
1. Make adjustments in the 2D window.
2. Follow the indicated guideline below:
Main Menu ▶ Sync (Ctrl + D)
2D Toolbar ▶ Sync (Ctrl + D)
※ Note:
Changes in a Pattern Color According to Synchronization
A Pattern that has never been synchronized appears in transparent.
A Pattern that has been synchronized at least once appears in red color, and a Pattern that its synchronization is currently activating appears in blue color.
Comments
The auto simulation makes the software nearly unusual. I move a single point and have to wait for 30+ seconds for the software to unfreeze. My iMac is newer than your oldest supported machines and has 32GB of RAM. And even with nothing else running, synchronization process is unbearable.
Is there a way to disable Automatic synchronization on latest version?
Automatic synchronization is absolutely unnecessary and horrible feature.
With complex pattern I have to wait after every single movement in 2D window, which makes working with clo3d a torture. Waiting for sync is now 90% of my working time.
I experience the exact same issue as @dosburglux. I am currently writing this while I wait for 'auto synchronization' to finish the auto synchronization that it automatically decided to do... I love the software but would not recommend it for any project with complex patterns. I thought it would have finished the auto synchronization by now but it hasn't which is why I continue to type. Happy auto synchronization everyone!
There it goes again... just waiting for auto synchronization....
And again
How many times does it have to fucking synchronize?!