Unfortunately we have no way to transfer licenses between different platforms so you need to purchase them separately.
The Mac App Store and the iOS App Store are not connected and the Mac and iOS (iPhone/iPad) are two separate and different platforms.

We offer two versions of the app, one built specifically for iOS and another built for the Mac.
Apple has a technology called Catalyst to help developers port an app from iOS to Mac but we will continue to develop our native version for Mac as it provides a better user experience and reaches a larger number of users including those with older Macs.