One filter for high/moderate/low by using groups

[lcs22]

So basically I have three categories, high, moderate and low. I want to have one filter on the top where the "high" category would include all high, moderate, and low data points(working with text no numbers). The next category would be "moderate", but only includes moderate and low data. Finally, the last would be "low", which just has the low category fields.

Thank you