i3wm makes it easy to assign applications to workspaces and save and restore layouts - which is e.g. useful for auto-starting always needed software.
To make these assignments, you need specific window properties so that you can tell i3 to assign [class="Your-app"] → 1
(in this example, Your-app
will be assigned to workspace 1).
In many cases this just works. However, there are also many popular programs that do not initially set the correct window class or other properties on startup, which can be frustrating. This cheat sheet aims to show the problems and possible resolutions (or worse: workarounds) for more or less problematic applications.