Connected Products allows you to create cart rules with percentage discount for pair of product. Main product based on "Attribute Set", additional product bas edon "SKU".

This module is compatibile with Magento Community versions: 2.4.

After installing the module, head to Admin Panel go to Marketing > Promotions > Cart Price Rules. Click on Add New Rule button to create your own rule.

Complete fields:

Rule Name – add rule name
Active – set active/inactive rule
Websites – select active websites
Customer Groups - select active customer groups
Coupon - select rule acvie with or without coupon

Set Conditions as below, where SKU is additional product:

Set Actions:

• Select Connected products discount rule as Apply
• Set Discount Amount (percent)
• Set Maximum Qty Discount is Applied To

Set the rule as below, where Attribute Set is for main product, SKU is for additional product:

On Product page with Attribute Set like at rule will be display box add to cart connected products:

After added to cart, on cart will be connected product with discount:

Composer

"repositories": [
    ...
    {
        "type": "vcs",
        "url": "git@git.auroracreation.com:aurora-modules/module-connected-products.git"
    }
    ...
],

"require": {
    ...
    "aurora/module-connected-products": "*"
    ...
},

composer update aurora/module-connected-products
php bin/magento module:enable Aurora_ConnectedProducts
php bin/magento setup:upgrade

Manual

{Magento root}
└── app/
    └── code

php bin/magento module:enable Aurora_ConnectedProducts
php bin/magento setup:upgrade

v1.0.0

* Initial
* Display box on catalog_product_view layout to add connected product 
* Main product base on attribute set
* Additional product base on SKU