Add to Angular global stylesheet. This approach seems best using utility class approach.
Create dedicated panel page css file. This approach is best for overriding component styles that would otherwise be impossible with global css or classes. Although this might become less of of an issue in the future when classes can be added using the inspector.
Open up the inspector and add css directly to elements that will be automatically saved. This approach works best for quick small edits on specific targets. The algorithm to convert the selected target to a css selector is somewhat limited at this point. However, it works on a mvp basis.
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