Hi,
in SE80 go to WebDynpro Component /SAPSRM/WDC_UI_PO_DOTC_IT and component configuration /SAPSRM/WDCC_FPM_PO_DOTC_OV and click on the start configurator button.
Enhance (more actions-> enhance) this webdynpro configuration by hiding the PROPOSE_SOS button in the toolbar (go through the built-in webdynpro tab and start scrolling).
V_PO_DOTC_BASIC -> ITEMS_TABLE -> ITEM_TABLE_TOOLBAR -> PROPOSE_SOS
Click on that and at the right side you will get the option to hide it.