Easeus Backup and PBD files

I use Easeus Workstation Backup and it creates .pbd files as a result of creating differential backups.

If I double click on these files it opens Windows Explorer which then opens the file as if it were an archive of sorts.

I've tried to use the "open with" option to set these files to be open by DO but it only opens a new lister not the file.

When I dug into the registry to see what was going on this is what I saw:

Windows Registry Editor Version 5.00

[HKEY_CLASSES_ROOT\pbd.file]

[HKEY_CLASSES_ROOT\pbd.file\CLSID]
@="{C1051DD2-472F-4B24-B47A-06769096CE34}"

[HKEY_CLASSES_ROOT\pbd.file\DefaultIcon]
@="D:\DiskTools\EaseUS Backup\Todo Backup\res\PBD-icon.ico,0"

[HKEY_CLASSES_ROOT\pbd.file\Shell]

[HKEY_CLASSES_ROOT\pbd.file\Shell\Open]
@="Open"

[HKEY_CLASSES_ROOT\pbd.file\Shell\Open\command]
@="explorer /idlist,%I,%L"

[HKEY_CLASSES_ROOT\pbd.file\Shell\Open\ddeexec]
@="[ViewFolder("%l", %I, %S)]"
"NoActivateHandler"=""

[HKEY_CLASSES_ROOT\pbd.file\Shell\Open\ddeexec\application]
@="Folders"

[HKEY_CLASSES_ROOT\pbd.file\Shell\Open\ddeexec\ifexec]
@="[]"

[HKEY_CLASSES_ROOT\pbd.file\Shell\Open\ddeexec\topic]
@="AppProperties"

Is there any way to create this functionality in DO?

Try turning on Preferences / Launching Opus / Explorer Replacement / Replace Explorer for all folders or the option below it.

Since it isn't a real folder, and is likely shown via a view provided via a shell namespace plugin, you'll probably have limited functionality within that folder. It'll probably be like having what you see in Explorer hosted inside an Opus window.