Currently, multiple asset search is only available in the classic search experience, not redesigned search.
If the Access Multiple Asset Search permission is enabled for you, you'll see the search option in the More dropdown. This search allows you to find a list of assets, like a list of filenames copied from a spreadsheet, in one search and based on specific criteria. You can search by filename or select any of the metadata fields available in the search. The multiple asset search will search through all assets based on your selections and return a maximum of 5,000 results.
To search, enter search terms separated by commas, semicolons, or carriage returns. You can also designate if the search should be an exact match.
For example, when you copy and paste filenames like "Happy Puppy1," "Happy Puppy2," and "Happy Puppy3" from a spreadsheet into the quick search, the search will return all assets with the corresponding names.