There are a couple of ways that you can configure Accelerate to default the Xero Account Code on invoice lines, both ways are configured via Settings > Xero Settings.
The first is by linking a Xero Account Code to a Accelerate Nominal Account, whenever that nominal account is used on an invoice line the associated Xero Account Code will be used:
The setup above shows that whenever the Nominal Account 200 is selected the Xero Account Code will default to 200 (Sales) and whenever the Nominal Account 210 is selected it will default to 260 (Other Revenue). These links can be updated or deleted by clicking the edit icon.
Alternatively, you can link a Xero Account Code to a Accelerate Cashflow Type. So whenever a cashflow of a certain type is invoiced the Xero Account Code associated with that type will be used:
The setup above shows that whenever a cashflow of type Documentation/Procurement Fee is invoiced, it will have the Xero Account Code 200 (Sales) as default. And if you invoice a cashflow of type Other Inflow then the Xero Account Code 260 (Other Revenue) will be used. Again, these links can be updated or deleted by clicking the edit icon.
Whichever way you use, the Xero tax type will default to the default tax type on the Xero account code selected. This can then be changed on the invoice line via Invoices > Edit Invoice.