Draft Documents have no impact on the GL report as you may have noticed. GL Reports show you data from GL entries, which are not created until a transaction is submitted.
For a ‘What-if’ report you’d probably have to write a custom python script report and fetch data from all your transactions that would impact the General Ledger including all the taxes incurred on them. Which will of course be complex.
I was just going to ask about this. I’m aware some other ERP systems have such a feature which makes it possible for reviewers to see the impact of Draft entries on account balances before approval. It would be really great to have such a report