Steam client parameters, consoles commands and variables

steam_console_params.txt

nClientBackgroundAutoUpdateTimeSpreadMinutes = "240" - Number of minutes to spread background auto-updates out over
@panorama_suggestions_view = "0" - 0 - default, 1 - no games or friends, 2 - just games no friends, 3 - some games and friends, 4 - some  friends no games
app_license_request - <AppID> - Requests a free licenses for this app if not already owned.
app_uninstall - [-complete] <appId>
-dumpvideostream - Dump the game stream as an elementary video file
-installer_test - changes installing a retail game to emit all files to install_validate/ folder instead of to the steam cache
-opengl - Use the OpenGL render for the UI
-fullscreenopengl - Use the full screen OpenGL render for the UI
-tenfoot - Start in Steam Big Picture mode
-bigpicture - Start in Steam Big Picture mode
-nobigpicture - Start in regular mode (force Big Picture mode off)
-steamos - 
-720p - Run tenfoot in 720p rather than 1080p
-480p - Run tenfoot in 480p rather than 1080p
-silent - Silent startup mode (tray mode only)
-fulldesktopres - Run tenfoot in full desktop resolution rather than 1080p, overrides -720p as well.
-windowed - Run Steam tenfoot mode in a window rather than a fullscreen borderless window
-store - Set the store URL
-language - Set Steam client UI language
-install - Install game from media
-pretend_ipt - Pretend system is IPT capable
-pretend_not_ipt - Pretend system is not IPT capable
-pretend_ipt_bad - Pretend IPT credential is bad
-forceservice - Run Steam Client Service even if Steam has admin rights
-accountrecovery - Perform account recovery
-community - Set the community URL
-forcecontrollerappid - Force a Specific AppID for Steam Controller Config - Prevents context/app switching from changing configuration
-debugbutton - Show debug button in content frame header
-testbutton - Show test button on main menu
-musiccrawltrack - Add menu to crawl track and print result to console
-enablealloobesteps - 
-storebeta - 0
-console - 
-noconsole - 
-supernav - 
-all_languages - show longest loc string from any language
-vguimessages - set to see debug vgiui2 messages
-fs_log - Log file system accesses
-fs_target - Set target syntax
-fs_logbins - Log the binaries we load during operation
-vguifocus - Print out details of which panel has keyboard focus
-ccsyntax - Spew details about the localized strings we load
-no-browser - unconditionally disables CEF
-cef-winxp - force running the WinXP compatible CEF browser
-no-dwrite - forces CEF to use GDI text even if DWrite support is available
-no-cef-sandbox - disables sandboxing in CEF
-disable-winh264 - disables loading winh264.dll
-voicerelay - Only allow 'relay' connections for voice (testing).
-log_voice - writes voice chat data to the logs/voice_log.txt file
-musicdbforcerebuild - Forces a rebuild and recrawl of the music database
-cafeapplaunch - Launch apps in a cyber cafe context
-complete_install_via_http - Run installation completion over HTTP by default
-lognetapi - logs all P2P networking info to log/netapi_log.txt
-tcp - forces connection to Steam backend to be via TCP
-single_core - Force Steam to run on your primary CPU only
-debug_steamapi - enables logging of Steam API functions
-dev - enables developer spew
-cybercafe - Forces cyber cafe mode for debugging
-vrdisable - Disable VR - never even try to load OpenVR DLLs
-vrskip - Skip VR initialization entirely no matter who asks for it
-vrforce - Always perform Hmd status check even if we crashed the last time we tried
-candidates - Show libjingle candidates for local connection as they are processed
-show-ssa - force display of SSA
-no-shared-textures - forces overlay to avoid sharing texture handles with game process
@sSteamCmdForcePlatformType = "" - Must be one of: [windows | macos | linux]
@sSteamCmdForcePlatformBitness = "" - Must be one of: [32 | 64]
@GCNameOverride = "" - 
@CustomBinaryRequestRetryTimes = "20" - 
@csecCSRequestProcessorTimeOut = "300" - 
@strCSNoCacheHeader = "no-cache" - 
@bCSForceNoCache = "0" - 
@bLANPeerConnectionTimeoutSec = "5" - 
@DepotBuilderParallelUploadChunks = "6" - 
@DepotBuilderMaxParallelUploadChunks = "24" - 
@DepotBuilderNumHTTPSocketsToMDS = "12" - 
@nCSClientRateLimitKbps = "0" - 
@bCSClientRateLimitUseDelays = "0" - 
@nDownloadLANChunkCacheSizeMB = "128" - 
@nDownloadLANPeerGroup = "0" - 
@nLANPeerRateLimitKbps = "0" - 
@cMaxContentServersToRequest = "20" - 
@cMaxInitialDownloadSources = "-1" - 
@cSecUploadDownloadRates = "300" - 
@LocalContentServer = "" - 
@CSInterfaceProxyUsername = "" - 
@CSInterfaceProxyPassword = "" - 
@cCSClientMaxNumSocketsPerHost = "8" - 
@sCSDSVirtualHostHeader = "" - 
@csecIncomingDataRatePeriod = "1" - 
@csecUpdateTargetNumConnectionsEpoch = "10" - 
@fMinDataRateToAttemptTwoConnectionsMbps = "0.5" - 
@fDownloadRateImprovementToAddAnotherConnection = "1.2" - 
@RunAdminInstallScriptsFromService = "0" - 
@cbPartnerUploadChunkSize = "1000000" - Chunk size to use for POSTing partner uploads
@bForceStreamUnsupportedApp = "0" - 
@StreamClientArgs = "" - 
@bEnableMovieRecording = "0" - 
@bEnableOfflineLogonTicket = "1" - If true, an offline logon ticket will be requested during logon if none is cached
@bRequireOfflineLogonTicket = "0" - If true, a valid offline logon ticket is required when logging in in offline or no connection mode
@bRequireSignedParentalSettings = "1" - If true, a valid set of signed parental settings is required when logging in in offline or no connection mode
@nParentalSettingsLogLevel = "4" - Control the amount of spew written to the parental log file
@csecFavoriteGameAccountCacheTime = "86400" - Control how often we refresh the account IDs in the game server favorites list
@nTCPLargeSendBufSizeMB = "16" - 
@bMsgErrorDump = "0" - 
@bEnableSpewThrottle = "1" - 
@bContentManifestUseProtobufs = "1" - 
@NetConnectionBufferMsgLimit = "1000" - Max # of message that will be buffered into a single zipped packet
@NetConnectionBufferThreaded = "1" - 
@nNetConnectionBufferZipLevel = "1" - 
@net_loopback = "1" - 
@net_backlog_time_allowed_sec = "5" - 
@net_backlog_bytes_allowed = "12000000" - 
@MaxOutstandingSendThreadItem = "1000" - 
@EnableUDPHistory = "0" - 
@cUDPSendRetries = "8" - 
@bDepotBuilderReadBufferSizeKB = "8192" - 
@bDepotBuilderUnbufferedReads = "1" - 
@cDepotBuilderFileChunkingThreads = "4" - 
@IOCPGetCompletionBatchSize = "1" - 
n@SpewThrottlePeriodMs = "1000" - 
@nSpewThrottleTriggerThreshold = "10" - 
@nSpewThrottleResumeThreshold = "3" - 
@nSpewThrottleUnconditionalTriggerCount = "50" - 
@nSpewThrottleUnconditionalResumeMs = "5000" - 
@nSpewThrottleNagFrequencyMs = "5000" - 
@cNetEncryptionHandshakeWorkMax_LowPri = "2000" - 
@cNetEncryptionHandshakeWorkMax_MedPri = "4000" - 
@cNetEncryptionHandshakeWorkMax_HighPri = "8000" - 
@cNetEncryptionHandshakeWorkMax_HighPri = "8000" - 
@cNetEncryptionHandshakeWorkMax_MedPri = "4000" - 
@cNetEncryptionHandshakeWorkMax_LowPri = "2000" - 
@cUDPSendRetries = "8" - 
@EnableUDPHistory = "0" - 
@MaxOutstandingSendThreadItem = "1000" - 
@net_backlog_bytes_allowed = "12000000" - 
@net_backlog_time_allowed_sec = "5" - 
@net_loopback = "1" - 
@nSpewThrottleNagFrequencyMs = "5000" - 
@nSpewThrottleUnconditionalResumeMs = "5000" - 
@nSpewThrottleUnconditionalTriggerCount = "50" - 
@nSpewThrottleResumeThreshold = "3" - 
@nSpewThrottleTriggerThreshold = "10" - 
n@SpewThrottlePeriodMs = "1000" - 
@bMsgErrorDump = "0" - 
@IOCPGetCompletionBatchSize = "1" - 
@nTCPLargeSendBufSizeMB = "16" - 
@bEnableSpewThrottle = "1" - 
@panorama_dragscroll_maxflickvelocity_vr = "8000" - Maximum velocity for a drag scroll flick in VR
@panorama_dragscroll_minflickvelocity_vr = "240" - Minimum velocity that the mouse must be moving as mouse up time to qualify as a drag scroll flick in VR
@panorama_dragscroll_maxflickvelocity = "8000" - Maximum velocity for a drag scroll flick
@panorama_dragscroll_minflickvelocity = "60" - Minimum velocity that the mouse must be moving as mouse up time to qualify as a drag scroll flick
@panorama_transform_parents_no_layer_if_no_perspective = "0" - 
@panorama_daisy_wheel = "ABXY" - Daisy wheel input mode: RS | ABXY
@panorama_debug_movies = "0" - 
@nCloudDetailsSimulatedFileCount = "0" - 
@bNewGameHelpSiteEnabled = "1" - 
@bCloudDetailsEnabled = "0" - 
@store_beta_mode = "0" - 
@store_country_code = "" - 
@panorama_trailerslideshow = "1" - 
@steam_alienfx_settings = "0" - 
@steam_controller_settings = "0" - 
@panorama_suggestions_web = "1" - 
@panorama_suggestions_view = "0" - 0 - default, 1 - no games or friends, 2 - just games no friends, 3 - some games and friends, 4 - some  friends no games
@panorama_mainmenu_web = "0" - 
@steam_alienware_hdmi_input = "0" - 
@panorama_backstack_focus_restore = "1" - 
@AppMRUSize = "20" - 
@bForceLaunchEula = "0" - 
@panorama_defaultinput = "dualtouch" - 
@nStatsMonitorScale = "1" - 
@nStatsMonitorSecs = "300" - 
@sBroadcastTune = "film" - 
@sBroadcastPreset = "" - 
@AllowSkipGameUpdate = "0" - 

Also check out https://github.com/Bluscream/Steam-Client-Docs ;)