Click the

Multiple Selection

check box to select multiple records. Press CTRL or SHIFT and click to select multiple records in the Unmerged or On hold tab. When two or more records are selected, the bottom two panes are cleared and only the following commands are available:

Accept the unmerged record as unique
Accept all records without a match
Accept all records without a match in the assignment list as unique
Put on hold
Queue for Matching
Reset as New Record
Reassign