There used to be an option in H264 exports to choose multi pass or single pass which I don't see anymore, and I can only assume it defaults to multi-pass since H264s take forever in this new version. Does anyone know if the option to choose single pass still exists and, if so, where?

The old h264 option was actually Quicktime 7 doing the export. Since Apple has killed that off with Catalina, it is no longer there. If you are on Mojave, you can install MC Legacy Components and then you still have your old QT exports.

The new h264 export option under the MOV section uses Avid's own Universal Media Engine. On my machines that is as fast as, or often faster than, a single pass QT h264 used to be.

UME MOV export options are limited, though (project size only, uncompress audio only), so in many cases it would be more useful to export to ProRes or DNxHD first, and then use a third party tool to create any h264 deliverables. I use Shutter Encoder these days. It is donateware, fast, cross-platform, and created by editors for editors. Also does things like re-wrapping, framerate pullup, etc. if you need it.

Thanks for the detailed answer!!

If you can, try an update to 2020.6. You can now scale the export. We often send HD1080 screeners at 960x540 so that's good. If you select Compression: H.264 you can then select Encode Mode: Variable Bit Rate Single Pass, then choose your Target bit rate and Max bit rate to suit your needs. On my machine the UME encode runs 3.x faster than the old QT export for similar size and rate. The only negative is the uncompressed audio of UME which is more data size than the video track. If Avid steps up to the plate with acc audio I would say they have hit this out of the park for many users. I think Job's suggestion of Shutter Encoder is a nice encoder but not having to double step would be great.

Thank you, DonE. I downloaded 2020.6 and was pleased to see that there were, in fact, more options including the abilty to perform a single pass. Do you believe it to be a disadvantage that I can only use Variable Bit Rate? If I'm being honest, I never really understood the difference.

An expert for h.264 I an not! I do know that when I use ffmpeg the default is using a quality method that is variable bit rate. I see very accepticle video for screeners  out of Avid VBR at 3 - 6 Mbps for 960x540 size, or even lower br. Again, up to your clients needs. 

This feature of better H.264 export is a VERY welcome, major addition that will save me hours and massive amounts of storage.  I'm now able to take a project, begin with all linked material, skip the a consolidate/transcode process entirely, AND go directly to a fairly-fast H.264 export.  I no longer have to render and output an entire 1-hour presentation just because I put a line of text / timecode window over the sequence.

Two major additions that would make this a nearly-perfect feature:

1. AAC audio in the export option
2. Background output (similar to Adobe Media Encoder).
(BONUS/adjustment): Text-input boxes to type in a specific target bitrate in the settings window. That slider is tiny!

Thanks Avid - this is a long-overdue, but very welcome, workflow change that has become absolutely essential now with QuickTime Reference no longer being a viable export method, and software such as Sorenson Squeeze being EOL.