When you use BTCapsule, you are literally using the Python script and running it from the Pydroid app on Android. This means you could create your own private key, and in the part of the code that says:

sender_create_priv = PrivateKey()

You can replace it with:

sender_create_priv = "LongStringOfRandomness"

Where LongStringOfRandomness is your private key in quotation marks. Then BTCapsule will build everything based on that private key.

Thanks for the encouragement! I hope it’s not too hard to use, and I can make it easier in the future.