The Object Sidebar

The Object Sidebar is on the right side of the main window.

Panels

The upper section is the Inspector which lets you edit the settings of the currently select objects
The lower section is the Object Palette which manages template objects that can be used in your document.

Resize the Object Sidebar horizontally

Locate the resize handle on the left side of the middle divider
Drag the control handle left or right

Change the vertical split between the panels

Locate the the middle divider between the two panels
Drag the control handle up or down

Tip:

Do not drag the resize handle on the left edge of the divider, this is for horizontal resizing only

Hide the Object Sidebar

Choose View→Object Sidebar →Hide Object Sidebar

Show the Object Sidebar

Choose View→Object Sidebar →Show Inspector