Modelling different expected dates for bills and invoices in Float can be done on both an individual basis and a bulk basis. Here we'll go through the options for doing this to individual invoices and bills. You can check out the bulk options here.
For setting an individual expected date first thing to do is click into the invoice you would like to update. You can either do this via the main cash flow by clicking into the relevant cell, selecting the 'Due' section from the budget popover and then clicking into the invoice/bill.
The 'Add new payment' option allows you to split the invoice down into multiple payments and you can check out the steps around this here.
The other option is to locate the invoice/bill in the 'Invoices Due'/'Bills to Pay' section. You can change the expected payment date via these three dots: