I was watching video about pickup height regulation and author was claiming that using screwdriver with magnetic tip and soldering gun close to guitar pickups may demagnetize them. Is this really dangerous?
It is possible to degauss pickups, but it's not likely to happen by accident, i.e. accidentally touching a pole piece with a screwdriver is not likely to noticeably degauss a pickup, but sticking it to a strong rare earth magnet for example, can. The previous link describes an instance of this very thing happening, plus Chris Kinman's instructions for how to use the same magnet to re-gauss the afflicted pickup. Pickup maker Bill Lawrence also advises us not to worry much about subjecting pickups to minor EMF.
So for the specifics of your question, using a screwdriver with a magnetic tip near a pickup will not measurably degauss them. There is some discussion about the magnetic field from soldering guns degaussing pickups, but no evidence that I can find. In an overabundcance of caution you could use a non-magnetic screwdriver and use a soldering pencil. Or if you must use a soldering gun, it's easy to keep the transformer away from the field above your pickup pole pieces, but don't worry, magnetism from a soldering gun will not "flow" down the wires and degauss the pickups.
Strong magnets are a BIG no-no especially on the vintage spec pickups. The magnets in the pickups are very sensitive to strong magnets and will ruin your pickups...trust me on this one. I was removing metal shavings from my pickups and ruined the top 3 of my bridge pickup. What blew my mind was when I went to play, I switched to the bridge pickup and the top 3 strings were silent whereas the bottomm 3 worked fine....now that had me scratching my head.
Yup, just did this. Trying to get the metal shavings out and used a 400 lb test magnet along all my pole pieces. Now some strings sound ok and some are noticeably quiet. Good news is pretty easy to just replace all the pole pieces. https://www.stewmac.com/Pickups_and_Electronics/Pickup_Kits_and_Parts/Pickup_Kits_and_Parts_for_Strat/Alnico_2_Polepiece_Magnets.html
At NO POINT does the author of the video claim that you shouldn't be using a screwdriver with a magnetic tip close to a guitar pickup.
Watch it again and listen more carefully: he claims that using STRONG MAGNETS DIRECTLY ONTO THE PICKUPS (to remove metal stuff from them) is a risk.
He does'nt say anything about magnetic screwdrivers.
FYI, "magnetic tip" screwdrivers have a very weak magnetic field so to make them harmless to electronic circuits. Thus guitar pickups won't be affected by using them.