The Bulk Product Editor now offers a feature to convert tags with a shared prefix into a metafield list.
In the editing interface, you can now select the desired field, such as "Size List" for example, and then choose the "Set from Prefix Tags" option. You would then specify the prefix for the tags you want to convert, like "size:". After running the operation, tags with the specified prefix will be aggregated into a new metafield list on the product page.
Example: If a product has tags like size:XL, size:M, and size:L, these can be converted into a "Size List" metafield containing a list of those sizes.
Learn more about converting prefixed tags to a metafield list