I did the same just by using a couple of element targets from withing uBlock origin.

Here they are for anyone interested:

www.facebook.com###u_jsonp_3_0 > div www.facebook.com###feed_stream_5a55a64611d#####0189168 > div www.facebook.com###stream_pagelet www.facebook.com###notificationsCountValue

The second one, you will likely have to figure out yourself - it looks like each feed stream has a unique id.