If the center channel is too low/the dialogue is difficult to understand, there are a number of things you can try to mitigate that within the Filter design:
Make sure that the Center is not supporting any other Groups.
Raise the overall Center Group level:
Select the Center Group.
Right click on the target curve → Convert shelves to control points.
Drag the whole target curve up by a couple of dBs. You can right click on the control points to remove them - making it easier to draw a flat curve.
Calculate and export the filter again.
Tip: You can store and load target curves in the Menu → Save/Load target curve.