Hi @KS86 
Add gr.update() at the end of your script in the script action.

var gr = new GlideRecord('cmdb_ci_network_adapter');
gr.addQuery('cmdb_ci', current.sys_id);
gr.query();
while (gr.next()) {
    gs.addInfoMessage("Previous Comments " + event.parm1 + "Previuos Domain " + event.parm2);
    gr.comments = "Parent CI desc updated as " + current.short_description;
    gr.update();
}

Regards,
Siva