My approach to yellow jackets is if they are in a location where not a nuisance to anyone I leave them alone. I know they have a role to fill in gardens. If they are someplace they could prove a danger to someone like my mail carrier, guests, then I treat or remove.

I couldn't leave them on my deck - my mother was highly allergic. Not the anaphylactic type with the dangers of breathing but she would have such a severe local reaction to a sting it would take prescription benadryl and a steroid to heal her rash and swelling. Every time. They can become more aggressive as days shorten and their food supplies dwindle, cannot imagine having them trying to share a cup of tea and sandwich on my deck and they will do that.

Tiny new nest like that one and I'd be tempted to go out after dark with a paint scraper or something similar, bucket of hot soapy water. Hold the bucket under the nest and in one movement, scrape it off to fall into the water. They will drown. If you had access to a hose with water pressure there you could knock it down with that but best done evening/night when its cooler and they aren't active.

My problem here on this property is more likely to be a ground nest. They are annual and don't return a second year so sometimes I can just leave alone. None at all yet this year and my fingers are crossed 😊

What we call yellow jackets here don't seem to have a 'waist' quite that defined - I would suspect seeing that on my own deck that I had some other kind of wasp.

Your balcony garden is lovely, I wouldn't feel badly about not sharing it with something very likely to sting.

These look like wasps and no one would expect them next to a railing.

I would definitely remove them. Be careful not to get stung.

Thanks for all the good advice. I ended up soaking it with a stream of water from a pump sprayer (hiding behind half closed patio door. I then used a long bamboo stick to knock of as much of the nest i could reach and finally used a brush with some detergent to scrub off the remainder on the reachable surfaces. I later saw that that the railing is hollow and the nest originates from inside that hollow. Anyhow, they were't back to building in the same exact place (at least when i checked a couple of days later but they started a new right at the bottom side of my metal railing planter! I now recognize that they aee paper-jackets, which are not as aggressive as yellow jackets. Anyhow, i dislodged that new nest in the same manner. I don't want to kill them but they really are a hazard and randomly bite while i am watering or doing other upkeep on the balcony. Unfortunately, dislodging the nests from the balcony hasn't made them go away. Apart from the bumble bee trying to get some food from my nicotianas this morning, some sweat bees, a random red spotted lantern fly or spider, they are the only critters in my garden. On the bright side, my petunias may die of heat but they don't get budworm or aphids anymore and i think the paper-jackets are to thank for that.

Get some WD-40. Spray it up into those spots where they like to nest. It comes with a straw, so you should be able to squirt up into the railing hollow. It can kill them, but more important, they don't like to build nests there after the WD-40 is there.