I would like to use Overpass Turbo to return all peaks over a certain elevation. I tried using the wizard, but I cannot figure out how to use the greater than (>) operator.
Overpass turbo wizard doesn't yet support numerical comparison. However, Overpass Api, the engine powering overpass turbo, already covers this feature.
This means that you need to provide the query in overpass ql format, and adapt it to include numerical comparison. You cannot use the wizard popup window in that case.
There's an extensive blog post that should answer all questions: http://dev.overpass-api.de/blog/numbers.html
It even includes examples for peaks over a certain ele.
Btw: adding this feature to the wizard is being discussed here: https://github.com/tyrasd/overpass-wizard/issues/4