The quickest way to contribute to your IRA from your taxable account at IBKR is to wire out the contribution amount to your bank from your taxable account and then to wire the funds back in as a deposit from your bank to the IRA account. Client Portal will allow you to correctly code it as a contribution.
IBKR supports the transfer of cash or positions between a taxable account and an IRA account on a case by case basis. Please note, an internal transfer from a non-IRA account into an IRA account is considered an IRA contribution, and IRA contributions can only be made in cash. The procedure requires review and additional steps including submitting documentation (proof of address, verification of ID and a call verification). These steps are necessary to validate such transfers. Requests for such a transfer must be submitted manually via ticket to IBKR Client Services for review. Select Funds & Banking as the Category followed by Manual Transfers, then type "Internal Transfer IRA" as the subject.
In some cases, transfers of cash or positions from an IRA account to a taxable account are not supported as they are considered distributions and may trigger taxes and early withdrawal penalties depending upon the age of the account holder and the amount. In addition, IBKR does not support any substitution of shares between an IRA and taxable account.