Can you add 'Tags' as an option to tasklists (and maybe events). Then one could have a tasklist 'Private' and a tasklist 'Business' and e.g. a tag 'Taxes' which can apply to both tasklists. Private task: File your income tax return with the tag Taxes and busines task: File your VAT return with tag Taxes.
This would help tremendously if you have a great nummer of tasks, makes it easy to find the right one.
If Tags are made available and searchable with tags, it would be even more useful for the software. A PC version would make the BC best management software.
maybe in combination with the Colors you already can choose.