I am so glad you ask for this topic. Systematic review users many times do not have the interest to assess the quality of an individual qualitative review. The CERQual approach addresses this issue.
Please see in the attachment the paper that describes this approach and the link of this working group.
The CERQual approach in its own right is not meant to be used as a quality appraisal tool, Rather it is a tool used to assess the confidence in the evidence of the individual review findings. One of the 4 domains it assesses is quality. CERQual does not dictate which quality appraisal tool to use. However I think the CASP tool is probably the most frequently used one. So in other words you have to do both the CASP and the CERQual as they address separate issues. Thats what I did for my systematic review anyway, which I hope will be published soon.
I disagree with Dr. Kieran. There is some terminology that it can be confused when it refers to the quality concept. From the GRADE working group perspective, you could find different terms to express the same idea about the quality of the evidence (QoE) such as confidence in the evidence, or lately, certainty in the evidence. These last two terms are "synonyms" for QoE. Please read the CERQual paper carefully because, perhaps, it can suit your requirement.