You've already selected an answer, but if there are more hallmarks, then you need to say it in a way that that is clear. Also, as you are clearly comparing and contrasting, you should adhere to a parallel structure, which you appear to try to do but fail to do. An example of how to do that would be:
"Some hallmarks of moderate disease are inflammation, O2 saturation
≥94%, and dyspnea, whereas of severe disease uncontrolled
inflammation, O2 saturation ≤93% (hypoxemia), and tachypnea."
Saying "some" is how you make it sound like they're not all the hallmarks.
Since you used the order "inflammation, O2 saturation ≥94%, and dyspnea" in the first half of the sentence, you would parallel that order in the second half of the sentence by using the parallel that order by using the order "uncontrolled inflammation, O2 saturation ≤93% (hypoxemia), and tachypnea," as opposed to switching the second two around like you did. Also, since you say "O2 saturation" as the second hallmark in the first order, you should parallelly make "O2 saturation" the second hallmark in the second order, thus putting "hypoxemia" in parenthesis, not the other way around. Finally, don't use a dash because it only muddles the parallelism since you didn't use a dash in the first half of the parallelism. You could use a comma, as a comma may demonstrate when you omit text you wish to remain implied, but it's not required, especially not when the omitted and implied verb is a version of "be" (e.g., "Beauty is truth, truth beauty" -Keats), so wouldn't use a comma there, much less a dash, but use nothing.
Two things to consider:
making the parenthetical "(i.e., hypoxemia)," which is more formal, the added abbreviation "i.e." being Latin for "id est," defined as "that is," used to explain what the aforementioned is, and always followed by a comma;
reexamining your use of "≥94%" and "≤93%" as they leave a gap of >93% but less than <94% (e.g., 93.5% O2 saturation would fall in that range) and as I have a hard time believing medical science actually leaves such a gap, so if, for example, "hypoxemia" is defined as "O2 saturation ≤93%" and hypoxemia is a hallmark of severe disease but not of moderate disease, then the second hallmark you give of moderate disease would be "O2 saturation >93%," not "O2 saturation ≥94%." (Basically, it would appear that either "≥94%" is wrong or "≤93%" is wrong, so you need to determine what the definition of "hypoxemia" actually is and adjust your figures in order to not leave a gap of just under one percent and create this no-man's-land of everything between 93% and 94% in your explanation of how moderate disease differentiates from severe disease.).