Can I add seasoning to the beurre manie? I want to thicken my curry but I also want it to have a lot of gravy/liquid - yet flavoured, not watered.

I'm going to make some beurre manie. Can I add curry to the mixture and then add it to the pan?

Maybe even cook some garlic and ginger in oil, then add curry, then buttter and flour. Is that ok? :P
Using roux - flavoured with curry powder and aromatics - is a well known, often used technique for japanese and chinese style curries. Your mileage may vary with beurre manie (known to be finicky), if results are not satisfactory try cooking the powder/aromatics in oil/butter and only then adding flour and whisking (classic roux technique).

Mind that indian and thai style curries use combinations of nut and seed pastes, coconut milk, yoghurt, cream, or just plain rich onion sauces/tomato stews to achieve thickness, sometimes helping things along with small amounts of cornstarch slurry - but rarely ever with roux and related techniques.