Welcome to the QuickBooks Community. I'll share details on how changing currency works and troubleshooting steps to ensure you're able to see the ZAF Rands currency on the list.
All your transactions must be accounted for in your books. If you have transactions in different currencies, QuickBooks' Multicurrency feature helps you record them easily without worrying about exchange rate conversions.
The ZAF Rands should on the list of Home currency and able to see this for changes.
Please note that you can only edit your currency when you have not yet activated the Multicurrency feature in QuickBooks Online. That's the reason ZAF Rands is not appearing on the menu. In case you have already turned on the Multicurrency feature, you can only change the home currency by deleting all your data and starting over from scratch.
However, if you didn't turn on the Multicurrency feature and you're unable to see the currency ZAF Rands, I recommend logging in to your QuickBooks account using a private browser. This is to rule out the possibility of a webpage issue, and private browsing doesn't store local files or cache.
Use these keyboard shortcuts based on the browser you're using.
For Firefox or Microsoft Edge, press Ctrl + Shift + P.
For Chrome, press Ctrl + Shift + N.
For Safari, hold down Command + Shift + N.
If it works in incognito, I recommend clearing the cache of your regular browser. This removes the history or log of sites so you can start with a clean slate. You can check this article to see the steps: Clear cache and cookies to fix issues when using QuickBooks Online.