Make it possible to disable all functions in a function app except a few specified ones

I have a c# function app that has over 30 functions.

I have the need to disable ALL functions EXCEPT one or a few specific functions that I want running.

An example of this is when I want to develop a new function in the function app, and I am running/testing the app locally. During this time I want to prevent all the other functions to fire off as it has undesired effects.

I know that there is the option to disable functions one by one in the local.settings.json file (https://learn.microsoft.com/en-us/azure/azure-functions/disable-function?tabs=portal#localsettingsjson) such as this:

`{
"IsEncrypted": false,
"Values": {
"AzureWebJobs.HttpExample.Disabled": true
}
}`

But this is not really a valid approach when there are many functions in the app (it becomes unmanageable).

**What I would LOVE to see is the following:**

- An app wide setting "DISABLE_ALL_FUNCTIONS" that disables all the functions in the app
- The possibility to then enable specific functions. We could use the [Functionname].Disabled?

It could look like this:

`{
"IsEncrypted": false,
"Values": {
"DISABLE_ALL_FUNCTIONS": true
"AzureWebJobs.HttpExample.Disabled": false,
"AzureWebJobs.QueueExample.Disabled": false
}
}`

Start with the local.settings.json example and the linked function-disable documentation to understand the existing per-function behavior. Trace how those settings are consumed by the host, then define and test the app-wide disable setting with explicit function exceptions; done means all unspecified functions remain disabled while the listed functions run.

Written by the indexing model from the issue text.