Yes, STEL Order allows you to set a currency as the main currency for the company, the prices of the catalog products or services will always be displayed in the company currency, as well as the reports, however, you can assign different currencies directly in the customer or supplier file by entering the customer or supplier file in the "Commercial" tab so that when creating documents for those customers or suppliers it will be in the currency they have selected.
You can also make the currency exchange directly within the document in the More information tab, you will have the Currency field and next to it the Currency rate field, the program takes the exchange rate based on the exchange rate of the day according to the European Central Bank, but you can change the exchange rate at the time according to the one you need to indicate.