I have a feeling that using the File Managers "Explorer" or "Super Manager", I came across the notifications source.
I didn't investigate it, so am unsure whether you can "clear data" or what options there might be .
It doesn't concern me that the "New Software" notification comes up every day.
In any case, everyone should have a good File manager app, - the first is for non rooted phones, but quite often you willnot be able to access a file - unless you pay for their rooted app.
However, the other, which also enables you to terminate apps. running is for rooted phones, but works on non rooted as well. Both have useful features.
Both are useful, and I use them frequently, especially to get rid of thumbnails, which still remain (if you have back-up on) when you delete a video.
If they are not deleted, your next video may adopt one of them as it's thumbnail in the Gallery.