The Editor panel's title bar should have "minimize" and "maximize" buttons, but when the current file's name is very long the label overflows and pushes the buttons off the edge.
I will fix this by truncating the title in the middle (when necessary, with "…") so that the filename fits.
This is fixed in trunk, r7094.
Fixed in the released version 3.4 of OmegaT.
Didier