I have a custom shape as such below.

The port connection is defined where the line starts:
{
id: 'port3',
shape: 'Circle',
offset: {
x: 0.915,
y: 0.505
},
// constraints: {
// connectionDirection: 'Bottom'
// }
}
However, the connection needs to go "down". Not "right". A lot of fiddling with the interface can force it to do down, but then just moving the object around will make it right again.
How can I force the port to only connect "down"? I looked at constraints as given in the commented code above however it does not work.
UPDATE: It seems like this solution ( https://help.syncfusion.com/wpf/diagram/port/port#connection-direction )is only available to WPF ? Is there a way I can get this functionality in JS?