Drag and drop pivot point, Rect Transform

Hi Unity-Com!

I'm pretty new with unity and doing the unity tutorial for a 2D RPG. I stuck at a seemingly easy point, where I have to move the pivot point of a mask per drag and drop, like here from point 4. But for me the whole thing moves and i cant select the blue circle.

Am i missing a shortcut?

I tried to change the "pivot" variables in the inspector, but the hole shape moves, instead of only the blue circle. i also googled for nealry 2 hours (sprites have a option in "sprite renderer" to set the sprite sort point from center to pivot to "unlock" the pivot point, but there is no sprite renderer in the UI-Image) and downloaded probuilder, with no progress.

please help!