This is really easy to achieve if you have more than 500 jobs/categories no tracking will convert and new tracking can be added post-conversion. If you have less than 500 you have two options:
Option 1: Find and Re-code
You can use find and recode to allocate tracking to the necessary transactions. Find and re-code in Xero is a fantastic tool to easily update or re-assign transactions.
Option 2: Monthly Manual Journals If there are too many transactions to update you could use a monthly manual journal to bring in the tracking information. Please run a job/tracking profit and loss from the source file and then use this to formulate the manual journal to incorporate tracking opening balances.
For additional information in regards to Manual Journals please see here .