This OpenCart v3.0.x related products module will give you unlimited power to relate your products to each other.
FEATURES
Relate products in bulk - many at once
Related products by price range
Related products by category
Delete Related products in bulk matching any search criteria

DEMO
https://ggwshop.com/oc3036/admin/index.php?route=extension/module/ggw_bulk_related_products
user: demo
pass: demo
OpenCart Related products by category

• Category to category related products
  
• Category to attribute related products
  
• Category to attribute Group related products
  
• Category to attribute Value related products
  
• Category to manufacturer related products
  
• Category to option related products

OpenCart Related products by Attribute

• Attribute to category related products
  
• Attribute to attribute related products
  
• Attribute to attribute Group related products
  
• Attribute to attribute Value related products
  
• Attribute to manufacturer related products
  
• Attribute to option related products

OpenCart Related products by Option

• Option to category related products
  
• Option to attribute related products
  
• Option to attribute Group related products
  
• Option to attribute Value related products
  
• Option to manufacturer related products
  
• Option to option related products
  
• Option to option Value related products

OpenCart Related products by Manufacturer

• Manufacturer to category related products
  
• Manufacturer to attribute related products
  
• Manufacturer to attribute Group related products
  
• Manufacturer to attribute Value related products
  
• Manufacturer to manufacturer related products
  
• Manufacturer to option related products
  
• Manufacturer to option Value related products

Requires Open Cart v3.0.x
Installs via the Extension Installer
Works with journal 3 theme and all other themes.
Documentation included.