Backgroundcolor of ...?

Hey guys,

Ive been following a yt series on a quest system which includes a UI showing the quests. However I ran into an issue with the backgroundcolor of one component.

My main widget is built like this:

The QuestTree is the important bit here, its entries are from another (objective) widget which is built like this:

Here is the result of it (with 2 quests):

I do not want the additional background on the quest tree and I have no idea where it comes from, I tried to hide every component in the objective widget and I still got the some BG, but in the TreeView in the main widget I did not see an option for the BG or anything like it.

In the yt video I watched there was no BG as well and I double checked all the settings he made are the same I have, so maybe its something in UE5? Idk any suggestions are greatly welcome.