Since this is listed as an "experimental command" your best bet for documentation is the man page.
$>az webapp up --help
Command
az webapp up : (Preview) Create and deploy existing local code to the web app, by running the
command from the folder where the code is present. Supports running the command in preview mode
using --dryrun parameter. Current supports includes Node, Python,.NET Core, ASP.NET, staticHtml.
Node, Python apps are created as Linux apps. .Net Core, ASP.NET and static HTML apps are created
as Windows apps. If command is run from an empty folder, an empty windows web app is created.
Arguments
--dryrun : Show summary of the create and deploy operation instead of executing it.
--location -l : Location. Values from: `az account list-locations`. You can configure the
default location using `az configure --defaults location=<location>`.
--sku : The pricing tiers, e.g., F1(Free), D1(Shared), B1(Basic Small), B2(Basic
Medium), B3(Basic Large), S1(Standard Small), P1(Premium Small), P1V2(Premium
V2 Small), PC2 (Premium Container Small), PC3 (Premium Container Medium), PC4
(Premium Container Large). Allowed values: B1, B2, B3, D1, F1, FREE, P1, P1V2,
P2, P2V2, P3, P3V2, PC2, PC3, PC4, S1, S2, S3, SHARED.
Resource Id Arguments
--ids : One or more resource IDs (space-delimited). If provided, no other 'Resource Id'
arguments should be specified.
--name -n : Name of the web app. You can configure the default using 'az configure
--defaults web=<name>'.
--subscription : Name or ID of subscription. You can configure the default subscription using
`az account set -s NAME_OR_ID`.
Global Arguments
--debug : Increase logging verbosity to show all debug logs.
--help -h : Show this help message and exit.
--output -o : Output format. Allowed values: json, jsonc, none, table, tsv, yaml. Default:
json.
--query : JMESPath query string. See http://jmespath.org/ for more information and
examples.
--verbose : Increase logging verbosity. Use --debug for full debug logs.
Examples
View the details of the app that will be created, without actually running the operation
az webapp up -n MyUniqueAppName --dryrun
Create a web app with the default configuration, by running the command from the folder where
the code to deployed exists.
az webapp up -n MyUniqueAppName
Create a web app in a sepcific region, by running the command from the folder where the code to
deployed exists.
az webapp up -n MyUniqueAppName -l locationName
Deploy new code to an app that was originally created using the same command
az webapp up -n MyUniqueAppName -l locationName