I’m keen to know this as well.
I have added a 'tag' to each expense that complies with the boost bonus ruling, so my accountant can run a report and see the relevant expenses to calculate at end-of-year tax time. It would still be nice to manually add the 20% additional deductible expense at my end. I checked the Xero community (ha) and their software can't do it and they recommend tagging expenses for the accountant to sort out. Keen to see if QB gurus have a recommended process.