@ZRaza
"For background: we have operating accounts for a family office that are externally managed, which transfer funds to accounts we manage. What is the best method to record this inflow of cash?"
Is the external account a business account? If so, they are assets of the business. Do you have those assets recorded somewhere else on some other balance sheet? If so, assign the same account to the transfer in that you assigned to the transfer out on the other balance sheet.
If you don't have those funds on another balance sheet, then that's an issue. This should be a simple account transfer between business accounts- Account A decreases (credit) by, say, $50K, and Account B increases (debit) by $50K.
If the external account isn't a business account, then assign the appropriate owner's/shareholder's/partner's equity account to the deposit in QB.