this seems to be workaround:

engine-setup --otopi-environment='OVESETUP_CONFIG/imageioProxyConfig=bool:True OVESETUP_VMCONSOLE_PROXY_CONFIG/vmconsoleProxyConfig=bool:True OVESETUP_CONFIG/websocketP
roxyConfig=bool:True'

(In reply to Jiri Belka from comment #0)
> Description of problem:
> 
> after initial run i had:
> 
> /etc/ovirt-engine-setup.conf.d/20-setup-ovirt-post.conf:OVESETUP_CONFIG/
> sanWipeAfterDelete=bool:False
> /etc/ovirt-engine-setup.conf.d/20-setup-ovirt-post.conf:OVESETUP_SYSTEM/
> nfsConfigEnabled_legacyInPostInstall=bool:False
> /etc/ovirt-engine-setup.conf.d/20-setup-ovirt-post.conf:OVESETUP_CONFIG/
> isoDomainExists=bool:False
> /etc/ovirt-engine-setup.conf.d/20-setup-ovirt-post.conf:OVESETUP_DWH_CONFIG/
> remoteEngineConfigured=bool:False
> /etc/ovirt-engine-setup.conf.d/20-setup-ovirt-post.conf:OVESETUP_CONFIG/
> imageioProxyConfig=bool:False
> /etc/ovirt-engine-setup.conf.d/20-setup-ovirt-post.conf:
> OVESETUP_VMCONSOLE_PROXY_CONFIG/vmconsoleProxyConfig=bool:False
> /etc/ovirt-engine-setup.conf.d/20-setup-ovirt-post.conf:OVESETUP_CONFIG/
> websocketProxyConfig=bool:False
> 
> thus:
> 
> - imageio proxy disabled

This is reconfigurable only in 4.2

> - websocket proxy disabled
> - webconsole proxy disabled

These two are not reconfigurable

> 
> then, 2nd run with:
> 
> # engine-setup --reconfigure-optional-components
> ...
>           Configure Image I/O Proxy               : False
>           Configure VMConsole Proxy               : False
>           Configure WebSocket Proxy               : False
> ...
> 
> 
> Version-Release number of selected component (if applicable):
> ovirt-engine-setup-base-4.1.5.2-0.1.el7.noarch
> 
> How reproducible:
> 100%
> Steps to Reproduce:
> 1. engine-setup (make imageio proxy disabled)
> 2. engine-setup --reconfigure-optional-components
> 3. check if imageio proxy is enabled/disabled
> 
> Actual results:
> previously disabled components are still disabled, user was not asked for
> confirmation
> 
> Expected results:
> user should be asked for new confirmation

Indeed, but only for components that were marked so (in the code).

In 4.1, we only have these marked:
- docker setup of cinder and glance (two items)
- dwh

In current 4.2, the docker plugins were completely removed, so we have:
- dwh
- imageio

If you want other components to be configurable, please open RFEs as needed.
The code does not prevent marking (and handling) other env vars (in addition to "components"), but each case requires a separate consideration.

You do not have simple means to know which items are "configurable". Feel free to open an RFE for this - should be pretty easy to add this to the log.
"Non-simple" means are to search for 'reconfigurable=True' in the code [1].

When you pass --reconfigure-optional-components, you can see which items were actually reset (from False to None) by looking, in the setup log, right after the line that has:

Stage init METHOD otopi.plugins.ovirt_engine_common.base.core.reconfigure.Plugin._init

> 
> Additional info:

[1]
# cd /usr/share/ovirt-engine/setup
# grep -r -C5 reconfigurable=True *
ovirt_engine_setup/ovirt_imageio_proxy/constants.py-    @osetupattrs(
ovirt_engine_setup/ovirt_imageio_proxy/constants.py-        answerfile=True,
ovirt_engine_setup/ovirt_imageio_proxy/constants.py-        summary=True,
ovirt_engine_setup/ovirt_imageio_proxy/constants.py-        description=_('Configure Image I/O Proxy'),
ovirt_engine_setup/ovirt_imageio_proxy/constants.py-        postinstallfile=True,
ovirt_engine_setup/ovirt_imageio_proxy/constants.py:        reconfigurable=True,
ovirt_engine_setup/ovirt_imageio_proxy/constants.py-    )
ovirt_engine_setup/ovirt_imageio_proxy/constants.py-    def IMAGEIO_PROXY_CONFIG(self):
ovirt_engine_setup/ovirt_imageio_proxy/constants.py-        return 'OVESETUP_CONFIG/imageioProxyConfig'
ovirt_engine_setup/ovirt_imageio_proxy/constants.py-
ovirt_engine_setup/ovirt_imageio_proxy/constants.py-    OIP_CERTIFICATE_CHAIN = 'OVESETUP_CONFIG/oipCertificateChain'
--
ovirt_engine_setup/dwh/constants.py-
ovirt_engine_setup/dwh/constants.py-    @osetupattrs(
ovirt_engine_setup/dwh/constants.py-        answerfile=True,
ovirt_engine_setup/dwh/constants.py-        postinstallfile=True,
ovirt_engine_setup/dwh/constants.py-        summary=True,
ovirt_engine_setup/dwh/constants.py:        reconfigurable=True,
ovirt_engine_setup/dwh/constants.py-        description=_('DWH installation'),
ovirt_engine_setup/dwh/constants.py-    )
ovirt_engine_setup/dwh/constants.py-    def ENABLE(self):
ovirt_engine_setup/dwh/constants.py-        return 'OVESETUP_DWH_CORE/enable'
ovirt_engine_setup/dwh/constants.py-

(In reply to Jiri Belka from comment #2)
> this seems to be workaround:
> 
> engine-setup
> --otopi-environment='OVESETUP_CONFIG/imageioProxyConfig=bool:True
> OVESETUP_VMCONSOLE_PROXY_CONFIG/vmconsoleProxyConfig=bool:True
> OVESETUP_CONFIG/websocketP
> roxyConfig=bool:True'

Thanks for trying and reporting, but please do not suggest this to people in general. People that edit their answer files should know very well what they are doing, and the above is basically the same. We do not document the answer files.