You can always change your accounting system in taxomate. To do so head over to Settings > Connections. From there you can remove and add your new accounting system. However, there are some things to keep in mind before you do so:
Bank Account/Credit Card Mappings: If you are switching from Xero/Wave to QuickBooks Online, there is a requirement to select the bank account/credit card where you receive Amazon payment and/or pay Amazon fees. QuickBooks requires this information to send all invoices.
Mappings: You will likely need to walk through Quick Setup again to map your accounts to the transaction categories. taxomate will need to create the default accounts again (unless you would like to use your own).
COGS/Inventory: Costs of Goods Sold and Inventory accounts will need to be re-created in your new software.
REMINDER: Once you confirm all your mappings and settings, remember to Reprocess all of your settlements prior to sending. This is necessary to make sure all mappings and settings changes are applied.