Sorry for this inconvenience.
At the moment, you cannot set or edit the currency conversions (Exchange rates) in Transcy by yourself because we get all data of the Exchange rate directly from European Central Bank system.
And it's always updated every day on this system to ensure that you're always provided the best quality and accuracy.
For more details about how to set up Currency, please visit here.
Hope this helps you :)
Should you need further support, please feel free to contact us via live chat or email us at firstname.lastname@example.org