In INDIA service charge is not mandatory, neither Govt says it is required, hence this is not required in MSD365.
For information- if in any hotel they add any service charge, you can ask them to remove it.
Note- I can give some customization idea if GST is added on service charge, you can use one seperate ITEM named as service charge, the custom code will add the percentage of from all the item values and then the GST is calculated in total along with the service charge item.
If GST is not calculated on service chrge then you can use load on inventory component and use service charge GL for posting.