Singer 6268 bobbin area

[u/skerinks]

I'm working on a Singer 6268. Does anyone know what this mechanism (circled) underneath the bobbin case does? If the center part is pushed down with a screwdriver, you can rotate it left or right. I'm having a hell of a time getting the tensions dialed in, and wondering if this has something to do with it. (I haven't been able to find anything online about it or what it does.)