I’d like to add my voice to those asking for the ability to set custom properties on line items.
In my case I am syncing deals to a e-commerce basket structure, I map baskets to deals and basket items to line items, being able to have the basket item id as a custom field in line items will make my life much easier.
It is a big data error, that information of products quoted in contacts cannot be copied. when do they connect that information? please, thank you
It is great to have custom properties for line items, although the ability to choose which properties to be displayed on creation is definitely a must. A sales rep now sees all the default properties which are not needed and are very frustrating.
Hello 
If you have ever struggled with manually adding line items to deal, say hello to the Add Line Item to Deal app we have released!
Key Features:
- Dynamically include a line item in an already existing deal;
- Capability to insert the following fields: SKU of the product to add, product’s quantity, line item price, currency list (USD, EUR, GBP, etc.).
Install the App: Head to the HubSpot Marketplace, install the Add Line Item to Deal app, and get started for free.
Say goodbye to manually adding line items to deals. Try the Add Line Item to Deal today and elevate your HubSpot workflow game!