For reference, I'm just going to reproduce wholesale a comment-discussion on the matter. It doesn't in any way answer the question, but I think it's useful background to collect into a place it can be found.
This came from a meta question workshopping a mainsite question; in the body of the meta Q OP noted "there's no official sandbox for RPGSE, so I'm hoping it's cool to get my question refined here."
Just for reference, it's definitely cool to workshop the question via its own meta question. – nitsua60♦ Jun 23 at 20:06
I was browsing through the site a bit and saw this post. For reference if you think a Sandbox might be a good idea on RPG.SE you can look at other sites such as WorldBuilding. Though it's not without problems and we are currently rethinking. CC @nitsua60 – Secespitus Jun 27 at 8:26
@Secespitus I just created and threw a [sandbox] tag onto this question: it seems to me that something like that hits a lot of the functional requirements described in WB (collects them all together, makes them easy to follow) without engendering some of the difficulties (lots of manual work to maintain list with links and delete "graduated" answers to maintain visibility, won't suffer auto-protection). I wonder if tags of [sandbox] and [sandbox-graduated] might be the solution over there? – nitsua60♦ Jun 27 at 14:32
Hmm... come to think of it, a [sandbox] tag might be problematic here, as it's a play-mode that gets mentioned a lot so might create confusion. Will have to ponder.... – nitsua60♦ Jun 27 at 14:37
@nitsua60 Monica already suggested something that in this discussion (inspired by shog9). If you ask me it introduces the problem that you don't have one post that you can link (or you make a different meta post that introduces user to search for a tag...) and it's more difficult to keep track of. I also think it's too big in the sense that some people will write big elaborate answers as suggestions and reading everything when you want to help new users is demanding more time from helpers. – Secespitus Jun 27 at 14:38
@nitsua60 But we are currently rethinking our Sandbox model. So yeah, it might work. I will regularly check back on how RPG handles it. Might be interesting to see. It currently looks like there is no "perfect" solution. PPCG uses a Sandbox like ours and just removed auto-protection from the whole Meta Site. As far as I can tell they are pretty happy. Maths uses something they call a Sandbox, but that's mainly for writing long answers that take time and having a place to dump them while working on them. So quite a bit different from our definition of "Sandbox". – Secespitus Jun 27 at 14:41
I think for RPG the sandbox is to just ask it on main site. If it's not quite up to snuff, it'll get closed, we'll work on it in comments and revisions, and then it'll get reopened. ☺️ – doppelgreener♦ Jun 27 at 15:43
@doppelgreener If I can interject a newbie's opinion here; I know to seasoned vets getting a question closed is nothing, but for newer guys it's pretty alarming. I'd much rather workshop in "private" - here in meta where votes don't affect my overall status - than endure downvotes from well meaning citizens that can majorly impact my ability to do things on this site. It just feels friendlier to work on meta first. – Alex Jun 27 at 17:14
@Alex Thanks for offering that up, that's some useful perspective. – doppelgreener♦ Jun 27 at 17:15
Links and upvote counts lost in translation, so it might be worth looking at the original comment-thread. Full disclosure: I have not pondered as I said I should--my bad =(