Frank Hamelly makes available a customization, courtesy of MS, to allow users to Resize the left pane in SmartList.
GP2themax – Helping users get the ‘max’ from Dynamics GP: Resize the left pane in SmartList
Reporting & BIInstall, Upgrade & Admin
Archived post from 2011. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.