Login with Google Account on device with different Google account

I've subscribed on my main device with my main Google ID (thus without a Locus Password)

For navigation purposes I configured another device with a different GoogleID, so that I can use that with less strict security settings. So on that 2nd device I'm using a different google ID on Android system level. I installed the Locus Maps app on that 2nd device and want to login to the app. However, I do not have a password and I also do not want to log in with my main Google Account on Android system level, because of that security concern.

How can I login to Locus Maps on my 2nd device so that I can enjoy my Gold subscription?

Thanks!