What is the best way to add attributes to the products like 'packing option', this is a field is for a process internally and not to show/modify by customers. I found that maybe I can use the TAGS field but I need the field required.
Also, I think the Variants field is not a good option due to I need a property field like SKU, price or Weight fields.
My name is Alison and I'm the Customer Success Specialist for Ablestar apps. I'm sorry for the late reply, but I thought I would reach out in case you haven't found a solution yet.
You may want to look into metafields (https://help.shopify.com/en/manual/products/metafields). Metafields can be used by apps and channels to track data for internal use, and are useful for storing specialized information, such as part numbers, customer titles, or blog post summaries.
If you choose to go with the metafields and have a large number of products, you can also use an app like our Bulk Editor (https://apps.shopify.com/bulk-product-editor) to modify the metafield data in bulk (https://support.ablestar.co/article/73-editing-metafields). It cannot create the metafields, but once you have them created it can help you fill in the data. The app also has a free version that allows for 5 free in-app edits and 5 free spreadsheet edits a month, so you could try it out without incurring any costs.
I've helped a large number of stores migrate their data over to shopify. I've had many store owners who require product attributes to be stored and displayed on their product page... Because I found this to be a constant pain point for a lot of store owners I ended up building out an app resolve this issue. (See solution #2)
To answer your question (as of today), there is no native way to add custom product attribute fields into shopify.
HOWEVER, there is a rather easy solution, explained below:
1) download a metafield app. Metafield apps allow you to create metafields, or 'custom fields', to store customized fields such as dimensions, height, width, length, color, etc.
TIP: If you have A LOT of product attributes, find a metafield app that allows you EXPORT & IMPORT these fields. If you don't do this, you're pretty much screwed if you want to migrate/move/bulk edit your products after the fact.
Price Range: These apps range from $0-$20 on average.
If you want to display the product specifications on your product page, see below.
2) Download this app to create the technical specification charts/ product attribute charts / product specifications chart (whatever you call them!):
This app is the only app that allows you to create multiple charts for all of your products/ product types. When you create the chart, you can automatically have it pull data from shopify fields (like type, sku), metafields (like dimensions, color), and even allows you to provide manual entry.