You can only see that effective fee rate during creation of the CPFP transaction by hovering your mouse over " [→ CPFP " near the fee rate.
Anyways, AFAIK 0.00sat/vB in Sparrow is only possible if the fee rate source is set to "Server" and your selected server "Bitcoin Core" is configured to relay 0sat/vB txns.
If it's the case (not a typo), I'd suggest you to set to standard minimum because even though you're be able to relay such transactions, most of your peers and miners will just reject it.