We would like to have VE enabled on the Sandbox on the Finnish Wikipedia. As the Sandbox is in Wikipedia namepace it's not possible to use it there. I found out that on en-wiki they created another sandbox for user page, because VE is enabled on user pages. Anyway, I think that VE is not going to be enabled on Wikipedia namespace since there are many forums or so, I wonder would it be possible to enable it for the Sandbox?
Topic on VisualEditor/Feedback
You can create a draft namespace (enWP ns118, ruWP ns102). For this namespace enable VE and transfer sandbox or create new draft:sandbox for VE in this namespace.
It can be configured per namespace, but I do not believe that it can be turned on for a single page within a namespace. Сунприат's suggestion of using the Draft namespace is one possible solution. Alternatively, you could create a "User:Sandbox" or just a subpage in your own userspace, and invite people to use that instead.
VisualEditor is offered there by default. Do you think that people really need a separate sandbox for it?
Well, the sandbox is supposed to be like a real article, so that we can try and learn our skills.
I have encountered this issue before on Wikipedia : the training or teaching stuff does not match the real stuff.
For example, I encountered this :
On a real article, I edit. I get the Visual Editor. I want to try something. So I go to the sandbox, and I edit. But now I get a different thing, which is not the Visual Editor. This is a problem.
Some months ago, on en.wiki, I suggested this. If you have a page like User:Sandbox you can update any relevant documentation to allow people to test in that page directly with VE by giving them the relevant URL to load it (the ?veaction=edit bit). Depending on which wiki you are talking about, there may be different ways to reach the sandbox. For example, on en.wiki, if I click on the link "Sandbox" in the top right bar, I get to my sandbox and then I have the option to click on Edit beta to launch VE. On other wikis, that link might open your sandbox in the wikitext editor instead; these wikis just have to fiddle with local configuration if they want to change this behaviour.
On en.wikipedia.org and on fr.wikipedia.org, I usually reach the sandbox by typing WP:SANDBOX.
Notice how the French community has provided for months now a prominent way to try VE. En.wp mentions VE at en:Wikipedia:About the Sandbox (and I'd guess, also in other places through which IPs and new users learn about the sandbox). It's entirely possible that the community could agree that en:Template:Sandbox heading needs further tweaking.