WiX setup creating a Registry key doesn't work when also using CustomActions - installation

Question

I have issues understanding the order of operation of the WiX setup.
When trying to create a Registry key to add a menu entry to Windows Explorer context menu and simultaniously
using CustomActions the Registry key will not be added.
If I however only try to register the key, it works (any CustomAction code is commented out).
In my Product.wxs I have set elevated priviliges with
<Package InstallerVersion="200" Compressed="yes" InstallScope="perMachine" InstallPrivileges="elevated"/>.
In my <Feature> I have
<ComponentRef Id="RegistryEntries"/> referenced.
This is the code for creating the registry key
<Fragment>
<Directory Id="TARGETDIR" Name="SourceDir">
<Component Id="RegistryEntries" Guid="*">
<RegistryKey Root="HKCR"
Key="Excel.CSV\shell\Use MyConverter\command"
ForceCreateOnInstall="yes"
ForceDeleteOnUninstall="yes">
<RegistryValue Type="string" Value="[INSTALLLOCATION]$(var.SolutionName).exe %1"
KeyPath="yes"/>
</RegistryKey>
</Component>
<Directory Id="ProgramFilesFolder">
<Directory Id="HSZLG" Name="MyConverter">
<Directory Id="INSTALLLOCATION" Name="$(var.SolutionName)" />
</Directory>
</Directory>
<!--<Directory Id="ProgramMenuFolder">
<Directory Id="Shortcuts" Name="MyConverter" />
</Directory>-->
</Directory>
</Fragment>
Now Im also using the following Custom Actions:
<CustomAction Id="UnregisterImportFormat" BinaryKey="WixCustomAction" DllEntry="UnregisterImportDefinition" Execute="deferred" Impersonate="no" Return="check" />
<CustomAction Id="PropertiesForUnregisterImportFormat" Property="UnregisterImportFormat" Return="check"
Value="app=AB;key=10000P1000" />
And call them in the <InstallSequence> like this:
<InstallExecuteSequence>
<Custom Action="PropertiesForRegisterImportFormat" Before="RegisterImportFormat" />
<Custom Action="RegisterImportFormat" Before="InstallFinalize">(NOT Installed) OR REINSTALL</Custom>
<Custom Action="PropertiesForUnregisterImportFormat" Before="UnregisterImportFormat" />
<Custom Action="UnregisterImportFormat" Before="InstallFinalize">REMOVE</Custom>
</InstallExecuteSequence>
It'd be gladly appreciated if someone can point out what I am doing wrong here.

Answer 1

There are difficulties with (deferred) custom actions running without impersonation as well as the HKCR key because HKCR isn't an actual registry location - it's a merge of the interactive user and HKEY_LOCAL_MACHINE\Software\Classes. This goes into detail:
https://msdn.microsoft.com/en-us/library/windows/desktop/ms724475(v=vs.85).aspx
and the custom action code is running with the system account (deferred, no impersonation) which is adding more confusion about which registry key you're creating. As that MSDN note says:
"To change the settings for the interactive user, store the changes under HKEY_CURRENT_USER\Software\Classes rather than HKEY_CLASSES_ROOT"
and I assume your code is attempting to use HKCR. Windows Installer is preferred for writing these registry entries because "it just works". Code running with the system account writing to HKCR is unreliable, so if you really must use code (and you shouldn't) then try HKEY_LOCAL_MACHINE\Software\Classes.