I’m not quite sure what you are describing, so I’ll suggest several things.
If the sidebar is not visible at all:
In the upper left corner of the modeling window, click the button under the three red - yellow - green round buttons to hide and show the left hand sidebar. Does this help?
If the sidebar is visible, but does not have the tool palette you want:
Select Rhinoceros > Preferences in the application menu.
Change the sidebar menu with the highlighted drop-down menu.
If you are using the command options dialog:
Perhaps you collapsed that tool palette to a zero height and the Osnaps panel is at the top of the sidebar. If so, click and drag at the top edge of the Osnaps panel to slide the divider between the Osnaps panel and the tool palette down.