After CDS data has been created in an environment, you cannot change the currency of the CDS data. If you need to change the currency, you need to delete the environment, recreate it from scratch and pick up the currency you wish.
With data being used and growing, this process may take you a month or 2 to complete, properly!
It may be hard, critical at the back-end to change the currency of the CDS data, but it is not impossible, nothing impossible I guess. I suggest that admins are allowed to change the currency of a CDS data from within the environment CDS settings, at least once.
It is totally unfair that I need to create a new environment to be able to change default currency. Even Twitter/Facebook allows verified accounts change their name, once may be. Allow us change currency once, please.
PowerApps supports the multicurrency system, each record can be associated with its own currency regard to a single currency, by using an exchange rate. That is known as thebase currency. However, after the base currency is set, it can't be changed any more.
Although this is by design, I will submit your idea to the Team.
As per the previous post, it is a change to the base currency that requires a new environment. This is because CDS converts all currency values to the base currency, and stores them in _base fields.
The main use for the base currency is to allow useful reports across currency values by using the _base fields. If you don't use this, there is no need to change the base currency. Even if you do want tot report across currency values, there are 2 other options that don't require a new environment:
Apply exchange rates in your report, working off the originating currency fields, which you could do with SSRS or PowerBI. This has an advantage, in that you get more control over when to apply exchange rates
Apply exchange rates in your report, working off the base currency, but just apply an exchange rate to convert it to whatever currency you want.