It is intended, macros take inputs either by the input order or by labelling them. If they aren't labelled than the first one is the filter for what tiddlers to add as tags, the second is the default tag to have open, the third is the state tiddler to use for the tags and the fourth is the class to use. Using your first example it would make normal tabs for all tiddlers tagged About and set the default tab to tc-vertical. https://tiddlywiki.com/#Macro%20Calls%20in%20WikiText and https://tiddlywiki.com/#tabs%20Macro may be useful.
You can make vertical tabs without listing the empty parameters like this: <<tabs "[tag[About]]" class:'tc-vertical'>> -- You received this message because you are subscribed to the Google Groups "TiddlyWiki" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/tiddlywiki. To view this discussion on the web visit https://groups.google.com/d/msgid/tiddlywiki/f192bf77-3b68-4efb-a6af-b84efd675bb3%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.

