As a Roblox developer working on a game that uses TeleportService very frequently and will have 15+ places, it is currently too difficult to test teleportation with emulated players and impossible to test with > two players.
To test TeleportService, I am using the standard Roblox player and the Windows app on an alt, although, this is not ideal as I am limited to testing with only two players. Ideally, I would be able to use Studio emulators with TeleportService although this is currently impossible.
If Roblox were to address this issue it would make testing TeleportService much easier, as I could test with more than two accounts and not have to interface through the outdated Windows app.
Personally what I’d like to see is a cross between local test servers (you can start multiple clients but they’re not live servers) and Team Test. Team Test servers are real live Roblox servers which is incredibly useful for testing (even solo), but they’re private and have certain features (unfortunately TeleportService too) disabled.
I think that in a prefect world Team Test would know how to let TeleportService work. For example, even if the restriction is that the place must be within the universe this is still sufficient enough for most people’s use cases.
P.s. for @OP you should be able to log in to multiple studio instances and Team Test from each but it’s very obnoxious to do. On top of that, TeleportService is disabled ofc which is obviously an enormous limitation when your goal is to test live features like TeleportService and make sure they work correctly before pushing code to live.
An official way to use multiple Roblox clients on one computer (2+) for development purposes
This is just one specific solution for your problem. There are other solutions, such as extending testing functionality in Studio / Team Create to allow for better testing with TeleportService.
Feature requests should focus on problems, not proposed solutions. Recommended to retitle the topic so it is easier to find for others and easier to understand at a glance (for staff and other readers) what your actual problem is (e.g. “Hard to test teleportservice locally without multiple accounts”).