Hmmm....well, I can see your irritated by it. I would be too.
And I'm really mean about having toys in the kitchen diner and my 'excuse' is that I'll trip over it when I'm cooking if it's on the floor (which is daft, because the toys rarely are where I'll trip on them) or they'll get food on them (but then that's a bit of a non-problem). It's my issue, not theirs.
Is this your issue? I mean, you say you have a shelf where toys that come to the table go? What's that for? Is it because you don't like toys at the table? Why not? (apart from that it's irritating ).
And I can see why the chain is a problem - is he actually swinging it round at the table? Could you say that there's too much on the table, and people/things are too close by for swinging, so when he's at the table, could he just fiddle with it, rather than swing it?
I always find the best approach (when I'm in the right mind!), is to say to myself 'what actually is the problem here? what is the actual reason I don't want them doing that?' and then, based on that 'is there another way round this? Can I change my thinking? Or come at it from a different angle to help change my DC's thinking?'
How old is he? If he's over 3, I reckon you could you sit down with him and say 'look, I can see you love your chain and it's really important to you but I really don't like you bringing your chain to the table because [insert real, rational reason]. Can you help me come to a solution about this, please, so we can both be happy? Have you any ideas?'
IME, children can respond brilliantly to things like this and be wonderfully creative in their thinking.
On another note - do we need a UP/TCS thread where we can post problems and ask for some collective, creative thinking? Lots of people have had some fantastic ideas on here - the more brains thinking, the more likely we are to get better at solving problems in the future?