I assume that you mean "In the case of changes in the top and bottom vertices and when changing the left and right width?"
It is not possible to set these sizes, but instead, you can set preferredSize, maxSize or minSize for the node of each of these regions depending on the situation you want to prevent, since the BorderPane areas change to their node size somehow. see " Change Range " in the BorderPane Document .
Maybe you should edit your question and give more details.
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