I have some long-ish timeline names, and they obscure a decent portion of the timeline itself. It's hard to see what's behind the label when that timeline is not selected because the text is heavy, and when a paricular timeline itself is selected, what is behind the label is completely hidden as the label background becomes opaque.

I don't know if it would be easier for you to change the font color (a grey, instead of black?), and to make the background transparent and show the timeline "selection" in some other manner, or to just expose a widget to choose such details to the users themselves.