I am sorry to break it to you but a cover letter is not going to make any difference in the rejection or acceptance of your application. You can get the cover letter written by Chatgpt and then make changes accordingly.
What actually matters is the documentation process where you have to be extra vigilant. Include the purpose of visit, duration of stay, enter dates, financial capability like bank statements or your payslip and all and most importantly, show your strong ties in India. This shows that you have the intent to return back to India. Your property documentation, job details, leave approval etc will be very helpful in getting you a Schengen Visa.