Update on the
oopsie experience...
I managed to get the dowel out, but because the wood is so soft half of it disintegrated and I had to
encourage the rest of it to come out. So what do you do? It's getting late in the evening, am not likely to find a tree growing bits of dowel and it's not the kind of thing you might have about the house like a few screws, washers, or nails. Thinking hard.. "
What have I got that is the same width ?....."

Then, some Kiwi ingenuity took over.... of course... A pencil! I cut the pointed end off with pliers, then measuring the length using another piece of dowel cut that off too. Tapped it into the hole just like the others, finished assembling the chair and it seems every bit as sturdy.