Can Bitcoin Core be made to display/enter amounts in USD or other fiat currencies? Every time I need to make Bitcoin payments, I have to switch many times between Bitcoin Core and my separate Bitcoin currency converter. For example, to see how much that transaction fee is in USD.
It would be very useful if it could be made to display a fiat currency instead.
Since this requires reliance on a third-party service, I understand why this is not built in.
However, can't I enter in the configuration file something like:
currency_converter_url = 'http://127.0.0.1/btcconverter/'

And then Bitcoin Core could make requests such as:
http://127.0.0.1/btcconverter/?satoshis=123456&amp;to_currency_code=USD

In order for my own script to output how much that many satoshis are in USD currently, so that it can display it to me.
Is this possible? It would be extremely useful.
No, this is not possible in Bitcoin Core. You will have to use a third party wallet software such as Electrum if you want this functionality.
There also isn't any standardized format for exchange rate APIs, so you will be limited to the exchanges that are already built into the wallet you select.