Not without an app. Excelify is great and has a free plan (can upload up to 10 items) and can do this.
Thank you for suggesting Excelify.
Indeed currently Shopify native import does not seem to support importing the Template Suffix field, but you can do this in bulk with Excelify.
The process is quite simple, you really need to construct a file with two columns:
As @gina-gregory mentioned - you can use Excelify for free up to 10 Items per import/export, so depending on how many Products you have, you could create multiple imports to update this in bulk for free, or you can take paid subscription plan, to update with a single import.
If you are interested in using Excelify or have any questions, feel free to contact us directly!
Confirms what I suspected regarding csv import option for Shopify - very disappointing how limited it appears to be
@Renars I did come across your app. Whilst it does seem to be very good and popular; from our perspective, it isn't a financially viable option at present. Maybe in the future