I like this. Anyone got any suggestions for the best way how to do it?

If this feature is added, removing an item that has been flagged as needing a citation should generate an edit summary that notes a citation was requested.

To brainstorm:
There could be a button right next to "add citation" with the title "request citation".
That button could bring up a dialog.

That dialog asks provides choices:
① This conflicts with what I believe to be true.
② This statement conflicts with source X.
③ This statement warrants an authoritative reference.
④ This statement is slanderous.

Afterwards there a box to alert people:
By default it's filled with the person who made the statement. The user can add additional people to be alerted. Those people get alerted via the standard Wikimedia alert system.

Finally there a button with [Create Citation Needed notice]

Once the Citation Needed notice is created, other users who see the notice can add their votes to the choices of the dialog. This voting allows for easy user engagement.

The easy solution is simply to add https://www.wikidata.org/wiki/Q7106262 or another item as a reference.

you need a process and team to add citations, not merely grow the "citation needed" backlog.

could we have a bot and bot runs to provide references to viaf & gnd
https://www.wikidata.org/wiki/Special:Contributions/SourcererBot

could we have a game to add reference statements
https://www.wikidata.org/wiki/Wikidata:Tools/External_tools

I wonder how much of this can be covered by T195052.

It would indeed be better than adding something to just a single item!

A high-level-ish take on this:

• Currently many items have no citation and while it would be nice to have one for every item, it seems that people focus on the most pressing first. As I got told in user research interviews e.g. "date of death" should always be sourced, particularly if concerning a recent date. I assume that other (implicit?) rules exist for other properties too (And if you know more rules that seem to be de-facto-standard, please send me a message)
• This means that a general "all things need citation" would not work.

AND

• As in T195052 suggested, a constraint based on "especially the ones likely to be challenged," might make sense.

AND

• Since citation or not might depend on the context and modeling, I guess a "citation needed"-ish thing, like a "reference-tag"+comment or so (I know, if at all, it is future stuff) since it could reflect the reasoning of people editing and reading.

How do we feel about this now with the existing constraint? Done? Anything else needed?

This is about flagging "citation needed" status on individual statement.

Right. My question was if this is still needed or of the constraint is enough.