I had 4 suggestions, one of which was a bug report. The bug seems fixed and 1 suggestion has been added already! (nice work )
So that leaves me with 2 suggestions:

Visually when changing the dimensions of a BSP brush I look at the color coding from the pivot to know what measurement I am about to change. Sadly you do not have the Red, Green, Blue color coding on those value windows. I added them in the preview below, a small addition, but would help imo?

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The 2nd would be a way to move the BSP brush per unit, for small adjustments, that you can use the arrow keys (which now currently move the viewport). Perhaps add a feature where you can press the alt-arrow key and it moves the BSP brush by 1 unit per click (or whatever grid size you have selected at the time). I believe Source engine had this and it made working with BSP super easy and fast. Currently it's tedious to move BSP precisely. If there is a way to do this already, I'm sure someone will let me know, if so, sorry