It would be phenomenal if Webflow recognized tags used in custom code and did not purge them when the Clean Up feature is used (in the Style Manager).
I suppose I’ll have to create a Style Guide page to avoid this issue (by creating a dummy Webflow element with the tag applied, said tag avoids the Clean Up purge), though I wonder if this tag-recognition and avoidance is a logical user experience Webflow should consider implementing. Cheers.