How can I add a custom app link to the admin side menu in my development store?

[sancuscommerce]

I have a development store and want to create a custom app to be used by this store only. In the store's admin, when I go to Settings -> Apps and sales channels -> Develop Apps -> Create an App. I get the API credentials and can make calls to the REST API to extract information. However, I can't figure out how to add a link to the admin side menu for this app.. ie, i want to have polaris pages so the client store can enter site specific information or click buttons to run jobs manually, etc.

I know how to do this with an app I create in the partner's dashboard during the installation process. But adding one of those apps makes my development store non-transferrable (I found that out the hard way). And this app doesnt need to be released to other stores nor the app-store.

[GerwinB]

@sancuscommerce 
We just ran into the same thing. After some research, we could not find any info or documentation on how this could be done with custom apps (it was possible with private apps).
So our conclusion is that custom apps do not support admin links.

Maybe someone from Shopify could confirm this?