I have an investment account with TD Ameritrade - where do I insert the management fee for my account?

Fees paid to brokerages for investment accounts etc. have not been deductible on a federal tax return since the tax laws changed for 2018 and beyond.   Such fees used to be included as the miscellaneous deductions subject to the 2% of AGI threshhold.

https://ttlc.intuit.com/questions/4482873-which-federal-tax-deductions-have-been-suspended-by-tax-reform

you can enter them as investment expenses on schedule A - for a possible state income tax benefit if 1)you have a state income tax and 2) the state allows itemized deductions). no assurance that even then you'll benefit from entering the amount