Lead/Contact - added in which all Lists

You can think of list membership as primarily a property of the list, not a property of the lead.

Obviously the two are closely linked, but Marketo doesn't automatically maintain a flat field -- a "reverse lookup", if you will -- with all the lead's lists (I assume you mean Static Lists here).

You can maintain such a list via a webhook: use a Textarea field that'll hold a semicolon-delimited value, trigger the 'hook on Added to List and Removed from List, pass the current value in the payload, get back the added/pruned value.

But it's not built-in. Think hard about whether you really need this functionality before going down that road. What are you using it for? Is there another way to go about it? (Not to say such a field is not useful, as we've found the need to roll it out a few times.)

(Also, tags on the Community are set using the corresponding input box, not hashtags.)