xDM

I am looking for something in Semarchy xdm to add attributes which can contain multiple values like arrays.
eg, Node entity should have an attribute to store multiple child values.

I can achieve this by adding a reference in Child entity to Node but in that case I am restricted to select only one Node in child but child can refer multiple nodes in my situation. So, I am looking for something in Node which can refer to multiple child entity attributes.

Depending on your needs, you can:

• Update your model to incorporate a many to many relationship (use the many-to-many picker to make the UI user-friendly) - details here
• Use a "multi-valued"-List of Values. This approach has more limitations but may fit your needs and is the easier of the two to implement.