You can press the bottom-right button to select an incubator, then press the egg you want to put in it.
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I've been curious for a while how long that's been an option. I first noticed you could do that I think a few months ago, but I was pretty sure that hadn't worked previously. I couldn't help but wonder how much longer than necessary I was doing it the hard way.
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I was scrolling slightly above the incubators (about the same height as the word 'incubators') to avoid pressing them but that's a much more foolproof way.