If so, Toolset has no backend GUI or else integration for its fields in the customizer, but I am also not sure how they could be used as fields are for content, not design.
Can you elaborate on what the goal is? Maybe we can help with a suggestion.
Which allows you to create the theme option. This is what Toolset offers at the moment.
if your requirement is other than what I shared, it will required custom programming as Toolset does not offer such native feature. You are welcome to contact any of our certified partners:
=> https://toolset.com/contractors/