I tried to edit this after I clicked 'Post' but I have tried addRowLabel.

dataSource: data,
dataSourceType: "json",
responseDataKey: "results",
height: "500",
width: "50%",
tabIndex: 1,
features: [
{
name: "Selection",
mode: "row",
multipleSelection: false
},
{
name: "Updating",
enableAddRow: true,
addRowLabel: "Add new message...",
enableUpdateRow: false,
enableDeleteRow: false,
startEditTriggers: "click",
editMode: "dialog",
columnSettings: [

For changing the rowadding area label, you may use addRowLabel option: https://www.igniteui.com/help/api/2017.2/ui.iggridupdating#options:addRowLabel, for changing the row edit dialog caption label you may use captionLabel option: https://www.igniteui.com/help/api/2017.1/ui.iggridupdating#options:rowEditDialogOptions.captionLabel. 

About moving the add row area in the footer of the grid, currently this is not possible as you may see in described in the following forum thread for your reference: https://es.infragistics.com/community/forums/f/ignite-ui-for-javascript/109558/move-add-new-row-to-footer-of-grid. You may submit a new product idea for this, following the steps listed in the previous link.

If I can provide you with further assistance, please let me know.