Easy2Boot and agFM can boot WinPE-based ISOs easily, however many of these ISOs require access to files on the 'DVD' drive once they have booted to WinPE.
Since these files are inside the ISO file on the USB drive, these extra utilities cannot be found by the miniWindows environment and you may find some Desktop and StartMenu items missing!
E2B and agFM can make this work however by using that fact that most WinPE's are built using WinBuilder which typically contain this extra startup code. When a WinPE made by WinBuilder boots, it looks for a volume containing a .ini file in the root (e.g. \WIN10PESE.ini) which specifies the path of an ISO file. WinPE will then find that ISO file and auto-mount it as a virtual DVD drive so that WinPE can now access the files within the ISO.
WIN10PESE.ini
IsoName=/_ISO/MAINMENU/Win10XPE_x64.ISO
E2B and agFM will modify these .ini files before booting the ISO (that is one reason why a write-enabled USB drive is required). The ISO filename should not contain spaces because some versions of WinBuilder cannot cope with spaces in filenames.
However, this only works if the WinPE contains this special WinBuilder startup code which looks for the special WinBuilder .ini file.
E2B and agFM also modify the \AutoUnattend.xml file in the root of the E2B USB drive - this file is automatically run if the ISO is a Windows Install ISO (but it is not usually run by WinPE ISOs).
c't Emergency ISO
Unfortunately, some WinPE ISOs do not contain this special startup code (e.g. c't Emergency Windows 2021). There are a number of ways around this: