There is no feature that allows one to set a specific "Risk" limit for an IBKR account but clients do have tools available to help manage the risk of open positions.
The Account Window displays real time account values which allows one to monitor the account's margin compliance.
A Margin Cushion Alert may be set to notify an account holder when the account's Excess Equity drops below a certain percentage of the account's Net liquidation Value.
Clients may use a Paper Trading account or the Risk Navigator to model changes in positions and see how that affects a variety of risk parameters in the account.