Unfortunately there is no way to do that currently through the application.
Just thought I'd add to the thread, as we have another prospect asking the same question.
They bulk purchase laptops and receive a batch of 50 laptops, which move from purchasing into the unassigned equipment.
They can multi-select items in tracked items and transfer them to a single asset. You can of course "Copy asset" and create x amount of assets.
Unfortunately, you cannot multi-select items and promote, which has similarities and of course risks (in the same way 'copy asset' creates).
What would be nice is that if you want to promote more than one asset, that it processes this in the background (without opening 50 pages for each promoted laptop).
There would be some considerations about how this should actually work. e.g. Should it run in the background for more than two, or maybe open a reasonable amount of new windows if manageable eg 3,5 or 10.