The self employed product does not allow you to create multi currency transactions, the USA forums may have been referring to the US product.
There are currently not any plans for this to be introduced, however our developers are always looking into customer suggestions. Please use the following link to submit feedback directly to them: https://selfemployeduk.uservoice.com/
This will submit your suggestion directly to them, and they will then look into implementing this in future updates, if possible.
Please also find attached a link to our product updates page: https://quickbooks.intuit.com/uk/product-updates/ - here you can check what features are upcoming, and sometimes when.