No, not yet
With the release of TWRP 3.0, the hope for flashing from adoptable storage was rekindled. But I had to first wait for a Samsung Galaxy S5 version of the recovery image. That arrived this morning.
Unfortunately, I then found out that the TWRP Manager had difficulty downloading the recovery ROM. So I had to download it myself and wait for the download. I rebooted my phone into TWRP and flashed the new version of TWRP on top of my recovery partition.
I then had to reboot and download a new ROM. I stored it on my SD card and crossed my fingers. Unfortunately, reading my adoptable storage from the recovery image didn't work. The option to do it was available. But TWRP couldn't read my encrypted partition. I guess I'm glad that it wasn't so easy to crack the ext4 filesystem encryption.
In the end, I had to reboot and move the file to the /data partition. Flashing worked from there. I guess that I'll wait until TWRP can read adoptable storage. But I do have a new version of TWRP. And it is quite flat with a Material Design look and feel. More importantly, there are a couple of cool, new features - even if reading my adoptable storage isn't one of them.