Gtk.TextBuffer.prototype.insert_interactive_at_cursor

function insert_interactive_at_cursor(text:String, len:Number, default_editable:Boolean):Boolean {
    // Gjs wrapper for gtk_text_buffer_insert_interactive_at_cursor()
}

Calls Gtk.TextBuffer.prototype.insert_interactive at the cursor position.

default_editable indicates the editability of text that doesn't have a tag affecting editability applied to it. Typically the result of Gtk.get_editable is appropriate here.