ListBox.AddRowAt
From Xojo Documentation
Method
ListBox.AddRowAt(RowNumber as Integer, Item as String, [Indent as Integer])
New in 2019r2
Supported for all project types and targets.
New in 2019r2
Supported for all project types and targets.
Creates a new row at row (zero-based), moving the existing rows below row down. For multicolumn ListBoxes, text is always assigned to column zero. The optional parameter indent specifies the amount of indentation of the row in hierarchical ListBoxes. The default is zero. It has no effect on non-hierarchical ListBoxes.
Example
The following example inserts a row in the 'ListBox. The code is in a PushButton.
Listbox1.AddRowAt(1, "Steven")