https://community.appian.com/discussions/f/general/12611/update-an-array-cdthi there, I&#39;m experiencing a little brain fade, so would appreciate a pointer or two ... I&#39;ve two interface&#39;s defined A and B. Interface A has ri!items defined which is a mapping to my CDT. I&#39;ve set it to allow multiple values. It has a sectionen-USTelligent Community 12https://community.appian.com/thread/56252?ContentTypeID=1Wed, 06 Jun 2018 05:13:03 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:89c6d342-d554-444e-be0e-527a489f040caratimHi Paul,<br /> Agree with umeshp. Passing the values using rule inputs through interfaces you can merger these 2 list of items.<div style="clear:both;"></div>https://community.appian.com/thread/56230?ContentTypeID=1Tue, 05 Jun 2018 15:48:35 GMTd3a83456-d57b-489c-a84c-4e8267bb592a:209eaaab-c9c0-4150-afde-96961cd7f63eUmesh PatelHi Paul,<br /> you can try following,<br /> 1. Pass ri!items of Interface A to interface B rule input<br /> 2. Once user add new item within interface B, say on button action, append this new item to ri!tems within saveInto e.g. saveInto:{<br /> a!save(ri!tems, append(ri!items, ri!newItem))<br /> }<br /> i hope it helps.<div style="clear:both;"></div>