Use this section of the Visibility form to change the visibility of individual blocks.
Visibility - Blocks
This page allows you to control which blocks are visible in each layer. A list of all the current drawing's layers are shown in the middle panel. For the highlighted layer, a list of all blocks are shown in the right-hand panel - those highlighted will be visible.
You can click on a block name to highlight only it, control-click to toggle it while leaving other items unchanged and shift-click to highlight a range of names. Right-clicking also allows you to: Select All, Select None, Toggle Selection, Select By Regular Expression.