This is unfortunately not supported to my knowledge. You could test via a data action the number of logged in agents before placing the call in a queue but you can't interfere with bulls eye logic, which should indeed be clever enough to skip the skill 1 if no agent is logged in with Skill1 in the first ring.
This is a basic feature that product management would need to consider so you need to log a feature request first.
It's very unfortunate that Bulls eye doesn't work with WFM, hence you need to think twice before using it for routing.
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Hichem Agrebi
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