Hey, buddy. Generally speaking, “center” is usually a fixed value, like 0.5 or 0. This serves as the baseline (median value) for displacement. For example, if your displacement median value is 0.5, then the parts of the texture with values less than 0.5 will appear to sink, while those exceeding 0.5 will seem to rise.
So, what you should do is determine a median value on your own, say 0 (usually this is the same as the median value you set when exporting from other DCC software). Then, achieve a satisfactory result by adjusting the texture or the parameters in the material graph, rather than fiddling with the median value. Set the median value to 0 or 0.5, and then play around with the material.