Please read the response by @Tut, Adding inventory items on the fly - #14 by Tut more spcifically:
So if you adopt the server or cloud editions, don’t be disappointed when you can’t find the “add on the fly” button.
There is no such button nor function in any of the Manager editions.
Please note that also for desktop version you can (right click) open a new window (as many as you like) in a browser which gives similar functionality as the Cloud and Server editions where you can have several instances open at the same time.
The only differences between the free Desktop version and the paid for Server and Cloud editions are listed at https://www.manager.io/compare/ more specifically of difference is:
- Multi-user Access
- User Permissions