This snippet informs how to add or allow custom tags in RTE

PAGE TS CONFIG AS FOLLOWS:

# Allow embed, parm, object and iframe tags, also see RTE parser code added in config.ts
RTE.default.proc {
allowTags := addToList(object,param,embed,iframe)
allowTagsOutside := addToList(object,embed,iframe)
entryHTMLparser_db.allowTags < RTE.default.proc.allowTags
}

TYPOSCRIPT SETUP SHOULD BE AS FOLLOWS

# Allow embed, parm, object and iframe tags, also see RTE setup added in rte.ts
lib.parseFunc_RTE.allowTags := addToList(object,param,embed,iframe)