Not possible in one step. (Although maybe there's a plug-in available ... I don't know)
Once the first export is started, you don't have to wait until it finishes before starting the 2nd export.
Yeah, pretty much what I do now. The problem is I sometimes forget that I need/want TIFF copies so I have to go back and do it again. Also, doing multiple exports really ties up my piece of junk PC. I would think this would be easy to add in future updates. Just add another couple check-boxes and select multiple file types when exporting.
You can use Exportant's "Fast Cache" feature to save time when exporting the same file with different settings (a free plugin I wrote).
It's an export filter which saves a rendered copy of the file being exported in a cache, if not there already (or develop settings / metadata have changed), and pulls it from the cache when present (so Lr won't have to re-render), so it takes 1/2 the amount of time to export 2 copies, 1/3 the amount of time to export 3 copies etc.
Unfortunately, it's not compatible with all export/publish services, e.g. Export Manager & Turning Gate Publisher.
It *is* however compatible with a lot of them, like:
Adobe's Hard Drive export or publish service.
My TreeSyncPublisher (export or publish).
Jeffrey Friedl's Folder or Collection publishing service (publish only).
If you're interested in saving your time but not your computer's, then just use Export Manager (without export filters), or a publish service (well, one publish service for each format..) - Lr will re-render, but it's one click to go..
Another option for speedy exporting of jpegs is PreviewExporter, which exports from the Lr lib preview cache - not appropriate for obtaining printable tiffs.
Thanks, Rob. I'll check them out.