Radar Relay only shows spaces in your wallet for tokens that you have. There are lots of tokens available and there is no need to crowd the wallet with empty symbols. If you get tokens in a trade that you didn't have before they will show up in your wallet automatically. There is no need to add token slots by contract address.
A recent purchase will look like this with the toggle not yet available to trade.
When you trade away a token so that you have a zero balance it will no longer show in the wallet tab.