Unity3D has a great core architecture – it’s easy to understand and use. However, it has some significant flaws.
One of the recurring problems I run into is that Unity requirs you to have precisely one “Scene” at any one time, but often you need to have multiple scenes at the same time. Problem? Yes, lots…
Unity 5 has some hacks to make it “sort-of possible” to have multiple scenes at once in-Editor.
Note: these were mentioned by Unity corp in August 2014, but aren’t available to most users yet
But they (appear to be) hacks: they help for a fraction of the use-cases. That’s fine: Unity has 10 years of software written on the assumption there is only one “Scene”; that’s an enormous amount of code to change! But can we do something about this?
TL;DR: I’ll put this on the Asset Store
If you just want a working solution, here’s the Unity Asset store page / support page, new versions will appear here first.
I’m using it myself on my own projects, and will do some beta testing with other people’s games. If it works well enough, it’ll go on Asset Store. I suggest reading this full post anyway – it’s an example of how to creatively solve small issues like this in Unity.
(if you’d like to beta-test this, tweet me @t_machine_org or email me (address at top of page). Unity Corp only let me have 12 beta-testers, so you’ll need to give me some info about what you’ll use it for, how soon, how much feedback you’ll give me, etc! Sorry :( )