Changing the plan or updating your Mirakl app to the latest version v2.0 required for recently released new features can be done by going to your Linnworks account>Application Store>My Applications.
Every subscription supports an unlimited number of Mirakl channels or marketplaces.
And there is only 1 Mirakl subscription needed per Linnworks account using it.
When the prompt asks for a new subscription it is only upgrading the existing subscription to the new subscription to be used in the future.
There is no duplicate subscription possible for the same app.
Linnworks account>Application Store>My Applications
And there please select the Update (or Manage button if you need to change the subscription plan) button on the Mirakl app:
You will be able to choose the needed plan on the second screen.