The EXPORT function is not available for an organisation budget, if it is the CONSOLIDATION of your Business Unit Budgets.
However, you can run a P&L with Projected Total report at an Organisation level to give you the values. Please note this is not in a format to be imported back into Calxa.
If you want to be able to use this to import back into Calxa for an alternative, organisation level budget, export it as a CSV file. Then you will need to remove any rows that are blank or relate to totals of sections so you are left with data that relates directly to detail level accounts only.