Multi Select table using checkboxes and utilizing the add and delete methods in the KeySetImpl class

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I have been looking at the Multi Select table recipe in the VBCS cookbook (\https://vbcookbook.oracle.com/?page=shell&shell=table-multi-select&table-multi-select=table-multi-select-start&table-multi-select-start=recipe)

I am trying to add additional functionality where I can dynamically add/delete rows to the selectItems observable.  For example, PageModule.prototype.selectSpecificRows = function () is hard-coding 2 keys to add to selectedItems.  I would like to use the add method explained here (https://www.oracle.com/webfolder/technetwork/jet/jsdocs/KeySetImpl.html#add) to add keys to the selectedItems observable, but I am struggling with the syntax.

Can someone possibly table a look at the cookbook recipe above and provide some insight on how to use the add/delete methods in the KeySetImpl class?