Nick here from Shopify. Great question.
The only way to apply a weight right now is for each product individually, it wouldn't be possible to do it via collections. Once each product has been assigned a weight you would need to create a shipping rate in your settings so the total weight of the order would be calculated to give the most appropriate shipping rate for your customer. One thing you could do is bulk edit the weights of a group of products. If you go to Admin > Products and then select the products you would like to edit the weight of and then select Edit Products. Once here, you need to select Add Fields > Shipping > Weight and the weight bar will appear on the right-hand side. Here you can adjust multiple product weight's at the same time should you wish. You can see an example of how this would look from the screenshot below:
You can also see the helpful guide Shopify has for this here.
Hopefully this helps!
All the best, Nick
Hey Yeah, thats what we are doing now, I just thought there might be a more efficient way as we are always getting a lot of items in.
No worries at all. I do like you're thinking on this though and will suggest you're feedback as a feature request to our development team for the future. It's feedback like this which helps them know what is on the mind of store owners such as yourself.
Thanks again for reaching out and asking.
This hasn't been implemented. Be sure to keep an eye on the Shopify Changelog for upcoming releases and features to see if comes up there.
@Thrift2U could you elaborate on why you think you need this? why does it have be automatic or on a schedule? aren't weights being entered when the product is created?
Or passed along when a product is duplicated?
How does the bulk editor, or spreadsheets from the back office not suffice?