ShippingEasy ("SE") currently has permissions which can be applied to each user. But regardless, users will have those same permissions for all stores. This is a big deficiency for SE customers that have drop shippers, or SE customers that are fulfilment services with many stores. 

Our fulfilment service uses SE. It would be a huge productivity booster to be able for handle our orders in their SE by categorizing, adding notes, adding tags, and cancelling orders.

But they definitely won't add us as a user, because then we can see all their other fulfilment customers' orders! We might even a competitor to one or many of them, so there's no way they'll make us a user.

FYI, they are not interested in accessing our SE account as it can't be integrated into their system.

Three years ago there was a very active discussion about user permission feature request here. But your product team completely missed the points about drop shippers that were made, and marked it as Completed. It was not! Examples: "Unfortunately, with the current set-up, they have access to everything we are doing, they can see the items that they are fulfilling, the items that other drop-shippers are fulfilling, as well as the items that we fulfill in-house." (Anthony)

"I am in a similar situation as the original poster, where I work with a dropshipper." (Misty)