To export the Budget to excel you would need to set up a Bundle containing a report for each business unit, and run the bundle, then export to Excel from there.
Use the P&L with Projected Total report, add a Bundle eg Budget by Projects, and select an individual Business Unit, review the report and add it to the Bundle one by one.
Optimise the Bundle for Exporting to Excel from the bundle screen.
NOTE 💬These reports cannot be used to IMPORT budget data back to Calxa. If you wish to make changes to a Budget in Excel, and then bring it back into Calxa, you MUST use the EXPORT Budget option