If, as I suspect, your issue is the size of the "grab-zone" at the edges of your windows, to make it easier to resize, the parameters controlling the gap/zone are not under the control of "Preferences".
The issue is one of Theme component internal construction, and I invite you to review the following two earlier discussions on this very topic:
... and how I eventually resolved it ...
... and, BTW, those are build-dependant, Distro and/or Theme, hence my original question.
