You are making changes to column width and changes are reflected when you re-logon to system.
Reproducing the Issue
Go to the Customer work center as an example.
Click on Accounts.
Increase column width.
Refresh screen or re-login
Changes are not saved.
In RUI, column width is auto set. This is to ensure column rendering will fit based on devices.
change of column width, auto adjust column width, column width, column size, column resize , KBA , AP-RC-UIF-FLX-FRW , UI Adaptation Framework , How To