What worked for us is an establishment of boundaries. If DD was asking too many questions and we needed a break or needed to concentrate on something else, we'd just tell her it's not a good time, let's talk about it later. DW also used the "ask your dad when he gets home" line. A VERY important component of this strategy was that, later on, we'd make sure to revisit with DD. "Okay, I've got time now, what was your question?" If we didn't, DD would have figured out that "ask later" was code talk for "ask never." Deliberate follow-up on our part gave her the confidence to accept that any delay was temporary, and not a put-off.
As for danger seeking... we let natural consequences handle that one. If she was doing something where she was an accident waiting to happen, we told her to stop, and she argued with us, as long as the chances of her doing any permanent damage were sufficiently slim, we'd allow her to continue. When she hurt herself, we'd do a quick damage assessment, and once we established she was basically okay, we'd say, "Told ya." She became REALLY receptive of safety information from her parents after a few of these.
Of course, a couple of years later DD decided it'd be a good idea to wear her bike helmet in the car, and strangers were giving DW ugly looks as a result, but that's what makes these kids so fun.
And just for comparison, she
took scissors to the cat in an effort to make a working Polyjuice Potion when she was four.
I hope you explained how difficult it would be to come up with boomslang skin and lacewing flies.
Yes... my DD's obsession with HP is in its third year now... why do you ask?
* If you have another parent in the home? Make time immediately upon that person's return so that you can decompress somewhere quiet.
I would choose another word here besides "immediately," because, having been on the other side of this, after dealing with work and commute stressors, this can feel very much like an ambush. Give your partner at least half an hour to ease into this. In our household, we find that dinner time makes for a natural transition period.
