I am currently running 2 versions of xcode. I recently upgraded from 9.3 to 9.4.1 and also xcode 10 beta 6 on High Sierra v.10.13.6. The simulators seem to work fine in xcode 10 beta 6 but are completely missing from 9.4.1 I have downloaded and installed additional simulators which show up in the simulators window list, however they are not added to the drop downs in the main project window and the devices list remains empty. I wondered if its simply that I have messed up something in the installation. I have tried to remove everything and reinstall and got the same problem.
Any advice would be great. If anyone who is also running two versions could recommend also optimum set up with installation etc. I can post more detail as required. I have added screen shots please follow the links.
[main nav - generic iOS device][1]
[empty devices panel][2]
[simulators panel][3]
[1]: https://i.stack.imgur.com/4qU4M.png
[2]: https://i.stack.imgur.com/SVLo0.png
[3]: https://i.stack.imgur.com/vavl1.png