Thanks for posting on PSC. If I understand your requirement correctly, there is a pagelist let say, "testPageList" and it consists of "pynote" property. Now the requirement is to add or append the value of "pyNote" at the last of "testPageList". Correct me, If my understanding of your use-case is wrong. Also, share the detailed description for better understanding.

If my understanding is correct and there is already a data transform "ListOfNotes" which is used to populate the pagelist with pyNote.

Usage

Use the Append and Map to action to append a page to the target Page List mode property and set the context to that page for subsequent child actions to map properties on that page. The target and source can be of different Applies To classes.

The Append and Map to action is equivalent to doing an Update Page action using the <APPEND> keyword. When the system invokes the Append and Map to action, it creates a new page in the target Page List property, without creating any embedded properties in that new page. Then, subsequent children actions create the embedded properties on the page.

When you select the Append and Map to action, the system automatically displays a child Set action, because no properties yet exist on the newly created page.

When using a Source that is a Page List or a Page Group property (using the each page in choice for the Relation), the  button appears next to the each page in choice. Click this button to specify a when condition rule for the Append and Map to action, so that a page from the source is appended to the target only if the condition is true. For example, when your target is a Page List property of PreferredCustomers, and you want to map data from an AllCustomers source Page List property only for those customers that are "preferred" customers, click the  button and specify a when condition rule named IsPreferred.

Refer it for more details:- https://community.pega.com/sites/default/files/help_v722/procomhelpmain.htm

Hope it helps you in implementing your use-case. Kindly notify if it does by marking this post as answered for larger Pega audience. 

Regards,

Asif