Hi Cecil,
It is true that is the column resize are is very narrow but I tested it using Google Chrome and Safari on Acumatica 2022R1 and had no problem to get it and resize. The quality of the mouse can also affect the ability to select narrow zones. I use a trackball mouse which gives no trouble.
Have you detected this issue with a specific web browser ? Also, did you notice if the issue is more evident on a specific form or report ?
The CSS is handled the same in all browsers unless there is some weird bug.
The problem is less of an issue for me but its certainly not very user friendly in general to less tech savvy users.
Lastly it serves no purpose to make it that small and actively makes the software worse to use.
So why is there no option to make it easier too use?