For meshing query you need to give more images of the geometry and issue.
In general what I understand it you want to change edge meshing of central square.
You can do that using edge sizing and you can also use biasing.
Please check following videos
Ansys Meshing Sizing:
https://www.youtube.com/watch?v=w4q6q8nKF3U
Please go through help manual for more details
Regards,
Keyur
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