The Fourth Button

[ectoren]

Back in Nougat days, I added a fourth softkey navigation button. A rather large circle on the right most side of the softkey navigation bar whose sole purpose was for Youtube. I lost the article that taught me how to put it on without root or app. I googled and googled and no dice. Anyone have an idea how to get rid of it?

 

[gozirra]

I believe that used to be part of System UI Tuner but was removed.