Hi @88889, welcome to our forum!
As far as I know, Google introduced this feature in Android 8.1 (it was introduced for Xperia devices in Android Pie as only one device has Android 8.1) and since the last update for the Xperia XA1 Plus is Android 8.0, you won't be able to see the battery status of your connected Bluetooth accessory in the quick settings menu.
If the Bluetooth accessory has an application that you can install from the Google Play store, you may be able to see the battery status in this application. That is the case for some of our own headsets at least.
I hope that answers your question!
