Option 1: Model the repayment as an income stream
This approach assumes that you have already taken a loan from your 401k. This indicates that your current 401k balance has already been reduced by the amount of the loan.
This approach also assumes that you know the duration of your loan repayment. If that is the case, you can model an additional contribution stream from your income to your 401k to simulate repayment.
Step 1: Go to My Plan > Money Flows
Step 2: Open the Recurring Contributions section
Step 3: Press on "Add a contribution +"
Step 4: Select your 401k as the destination account
Step 5: Enter your monthly payment amount
Step 6: Enter the start age and end age (based on the account holder's age)
Step 7: Press Save
Option 2: Model the repayment as an expense
This approach assumes that your current 401k balance reflects the total after you repay the loan.
This approach also assumes that you know the duration of your loan repayment. If that is the case, model a debt with the description of loan repayment for the duration of your loan.
Step 1: Go to My Plan > Debts
Step 2: Open the Non-Mortgage Debts section
Step 3: Press "Add a non-mortgage debt +"
Step 4: Select that this is an "Other" debt
Step 5: Select that you will manually enter this loan
Step 6: Enter a descriptive name
Step 7: Enter the current balance
Step 8: Enter the interest rate, likely 0%
Step 9: Enter your monthly payment
Step 10: Press Save
Monthly payments will continue until your loan is paid in full.