I understand not all the variant can be done in bulk action for multiple items such as SKU.
But still, there are variant that can be done in bulk action.
Among those, what I need most in bulk actions are;
(1) Group adjustment
I know ungrouped items can be grouped to new or existing group in bulk.
The difficulty is group change in bulk.
At this moment, group changing for even single item is difficult.

(2) Adding item in Sales order
Search function for item now is fine.
But still it need to be repeatedly typed even for similar multiple items.
For example, when I add 'shoes-black-160mm' and 'shoes-black-170mm' in sales order I need to type part of it and drag down dropdown list to find right one as much as the number of items.
How would be inefficient when I add same items, colors, price, quantity but just different in sizes from 110mm to 180mm with 5mm step increase!
As someone already suggested here, I hope problem can be solved by enabling first item to be duplicated and user just can be edited part of it.

(3) Data reset
Before applying your service to company task. users might try it with mock data to make sure that all the functions and service is fit to their need and worth to pay.
Once user is sure it can, mock data need to be deleted.(sales order, items and etc)
If there is reset function to initial status, clearing all the data it would be convenient.

Your service is cool.
Not too simple and not too complicated.
Please have in mind that what users need is not just many functions but functions that is clear and easy to use.