Hello and thank you for your comment and for using XWidget
The dev added a notification window that appears on the first run installing XWidget. Also has been written in the description of the app on PS since from the first moment. Also exists in the FAQ app's menu for very long time, with the instructions. (!)
For who uses XWidget for a long time adding a persistent notification it will be only annoying. After Android 6.0 the OS became more aggressive and especially on 8.0 and 9.0 it's a must have for apps like XWidget or the rest as you mention.
Unfortunately many users are lazy to read the descriptions or open all the options bypassing all the above.
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