Like this:
Assumptions:
you have $500 in your US bank account
you have €0 in your EURO bank account
your EURO account is setup with as the Currency on the Journal
Your Bank Balances would then show like this:

First, you will record an INTERNAL TRANSFER of funds OUT of your USD Account:

Next, you will record an INTERNAL TRANSFER of funds INTO your EURO Account:

Your balances at this point will be:

Note: because Odoo has not yet been given the exchange rate the bank used, it will not show the same amount. You rectify this during Bank Reconciliation. Just like a Customer Payment you have not yet verified, the Internal Transfer amount has not yet been verified (so doesn't show up in your GL yet).
Reconcile your USD Bank Account:


Reconcile your EURO Bank Account:

Note: You need to show and populate the Amount Currency and Foreign Currency amounts. You only need to do this for transfers between accounts - and only for the part of the transfer needing to be converted to a different FX amount than Odoo would have done (if left blank, Odoo would book this at €84.18)

Balances after both Bank Statements have been reconciled:

Balance Sheet:

Journal Entry from the Bank Reconciliation process on the EURO account:
