To create a recurring discount on a service -

Start by creating the "fee". Select New Fee, select the Business Line, select the recurrence as Recurring.

The fee requires a name, a value and a pricing period. With this fee being a discount, the value in either case needs to be a negative (-$5.00). This will be considered a Sub-Item (Pricing period must match the pricing period of the service)

Once you create the fee, select the 3 dots next to the fee and select Link

Select which service(s) you want the discount automatically associated with

Once this is applied, then as you add that service to a customer, the discount is defaulted to on.