Usage of combination price rule type to apply pricing rule functionality for a discount at orderline level

Answer

Example Scenario:
If an order has following order lines:
Frame : 1 Qty
Lens : 2 Qty
VA : 1 Qty

Then , Apply the following percentage discount adjustments:
Frame : 10%
Lens : 5%
VA : 50%

Product is allowing to apply only a flat 10% of on all the items and not giving the flexibility to add a different discount at the line item level.
When an order has the above combination of Items and quantity, you should be allowed to choose to give 10% discount on Frames, 5% discount on lens and 50% on VA.

While product can not fulfill the mentioned desired functionality using a single pricing rule but it can by using several pricing rules; wherein each pricing rule requires all the three items on the order to be applied and then each pricing rule applies a specified discount to one of the items.

With ExclusivityType set to RULE_TYPE_ITEM or RULE_TYPE_ITEM_INST, only one rule will get applied to an item or item instance giving the desired functionality with regards to exclusivity.

Sample managePricingRule API input XML:
<PricingRule Currency="USD" Description="Pricing Rule for frame" DistributeAdjustment="N" EndDateActive="2022-04-30T16:15:57-04:00" IgnoreRuleOnPriceLock="Y" IsCouponRule="N" IsCustomRule="N" IsItemAttributeValueRule="N" IsItemRule="Y" ItemOperatorCode="ALL_ITEMS" OrganizationCode="Ent"
PricingRuleName="pricingRuleFrame" PricingStatus="ACTIVE" RuleCategory="PRICING" RuleType="COMBINATION" StartDateActive="2013-04-02T16:15:54-04:00">
<PricingRuleTargetAttributeValueList/>
<PricingRuleTargetItemList>
<!-- the items that will be discounted -->
<PricingRuleTargetItem TargetItemID="F" TargetUnitOfMeasure="EACH"/>
</PricingRuleTargetItemList>
<PricingRuleItemList>
<!-- the items that need to be on the order for the pricingRule to apply -->
<PricingRuleItem ItemID="F" Quantity="1.00" UnitOfMeasure="EACH"/>
<PricingRuleItem ItemID="L" Quantity="2.00" UnitOfMeasure="EACH"/>
<PricingRuleItem ItemID="V" Quantity="1.00" UnitOfMeasure="EACH"/>
</PricingRuleItemList>
<PricingRuleActionList>
<!--the discount-->
<PricingRuleAction Adjustment="-10.00" AdjustmentType="PERCENT" ChargeCategory="Discount" ChargeName="Discount" WhenToApply="EACH_COMBINATION"/>
</PricingRuleActionList>
</PricingRule>

Similarly other 2 pricing rules can be created for remaining 2 items (PricingRuleTargetItem) that will be discounted.