Right now, I’m running 5.5M1 although I’ve noticed this problem on other versions.
In the upper right part of the IDE, there’s a tab with a dropdown icon, the perspective name, and a >> icon. Available perspectives are split between the dropdown and the >> icons according to some formula that remains mysterious. When I’m debugging, I want to switch among DB explorer, Java, and Debug perspectives. The perspective selection moves between the icons so I often guess wrong the first time I try to switch to a perspective. It may be useful to have an icon with the “active” perspectives, but there should be an icon with “all available’ perspectives, even it they are also on the “active” list.