Android SeekBarPreference custom view

I'm trying to implement SeekBarPreference into my preference XML. I have attempted to use MrBIMC seekbar (https://github.com/MrBIMC/MaterialSeekBarPreference) which mostly worked but due to it being old, there were some issues I had to come up with ugly solutions for.

<SeekBarPreference
android:defaultValue="5"
android:dependency="a_different_preference"
android:key="seekbar_key"
android:max="40"
android:summary="Select your value"
android:title="Seekbar value"
app:iconSpaceReserved="false"
asp:min="1" />


The above code does mostly what I want, except I can't figure out how to add a measurement value.

sample:msbp_measurementUnit="km"


The above is what is used in the MrBIMC library to set a unit after the value, but can't achieve anything similar natively.

Lastly, in my preferences.xml, I get the error "Element SeekBarPreference is not allowed here" which is preventing the IDE from showing me any suggestions to get what I am after.

Edit:
Since asking this, I have learnt that the native seekbarpreference does not seem to have the ability to add a measurement unit after its value... So, how exactly can I create a custom view, that looks and behaves the same, but has the ability to input a measurement unit?

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