Most GIMP filters are doted with a variety of parameters which control
the filter effect. Because it is often difficult to know in advance
how much of a certain filter parameter you want to apply to an image,
a little experimentation is usually necessary. Unfortunately, the
GIMP filters are three menus deep in the Image menu. Thus,
experimenting with a filter means finding it in the appropriate
submenu, evaluating its effect on the image, undoing the effect if it
is unsatisfactory, and reapplying the filter with new settings.
Repeatedly searching for the same filter in the system of image
submenus can become annoying. One way to limit the annoyance is by
tearing off the filter submenu, making access to it more rapid (see
1.1.2 for more on tear-off menus). A more
direct method, however, is by using the keyboard shortcut for the Re-show Last function. The shortcut is
A-S-f. This function recalls the dialog of the last filter
applied to the image, along with the previously used dialog values.
Thus, with two keystrokes, C-z followed by A-S-f, a filter
effect can be undone and redone with new parameter values.