N1ck Hi Nick,
You should see the Automatic top up option at the end of the flow after doing a manual top up for the first time. It will say "Automate future top ups".
There is a handy post here on how to set that up https://together.bunq.com/d/1974-automatic-top-up
I just tested myself and it worked 😊
If you're still not seeing it, feel free to jump into our Private Matters chat and let us know, there might be a bug somewhere that we aren't aware of. 🐞