@Roanna Kay Boni @HariniDhanabal The attachment icon on sow sidebar cannot be deactivated or hidden via client script as compared to native UI. In SOW under attachment tab should not show upload button when incident is closed, if that's not the case you can raise a HI Case. However if you still wish to hide the attachment tab completely for closed incident you need to write a scripted screen condition for this tab, refer screenshot to navigate to screen and create screen condition
<your-instance>/now/builder/ui/page-settings/pc/728ec88c43fa2110f20fff53e9b8f278/0bd6c17843b47110cc25ff53e9b8f288/params/view/4bd685bc43b47110cc25ff53e9b8f27c
Note that using screen condition with tabs and side panels may cause performance degradation, so avoid using it unless very much necessary.
Please mark my answer helpful/correct if this helped to solve your problem.
