Because 4th Dimension (4D) is an Multiple Document Interface (MDI) application it is possible for a window (e.g. a Form Editor window) to be so large that it does not fit on the screen and, thus, the resize anchor cannot be accessed. This can happen when changing the resolution of the monitor or when moving the database from machine to machine.
There are two ways to fix this, one for MacOS X and one for Windows.
Maximize the offending window by clicking the "Zoom" button and then grab the resize anchor (bottom-right corner) and resize the window. This sets the new "un-zoomed" size for the window.
-Hold the COMMAND key.
-Hold the right-mouse button (or CTRL-click) and drag the window.
-Hold the CTRL key
-Press (and hold) the left mouse button (make sure the cursor is over the offending window)
-Press (and hold) the right mouse button
-Drag the window up and left until the resize anchor can be seen
You may need to perform several "drags" depending upon how large the window is. Once the resize anchor is visible, resize the window as much as needed. If the window is still mostly offscreen, repeat the above steps bug drag it down and right instead. Again, you may need to repeat the resize/drag operation depending upon how large the window was to begin with.