It would be nice to have, alongside the 'Repeat "<Filter>"' and 'Re-show
"<Filter>"' an option to Repeat the filter BUT with the ability to set
Opacity and Mode variations before applying it.
A simple dialogue showing Opacity and Mode settings would pop up with
OK/Cancel buttons.

This would be very useful when having applied a Filter that was nearly
right, but needs some tweaking.

Here is some (hopefully) relevant IRC discussion:

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<UnNamed> mitch: it is not a macro
<UnNamed> mitch: it is way faster, doing it by recomputing all again with a
different opacity is a waste of time
<brix> mitch: but the call to g_signal_stop_emission_by_name() was actually
added by yosh
* brix hides
<mitch> UnNamed: actually it corresponds to the last
gimp_image_apply_image() call with varying params
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<UnNamed> peppo: yes, why not? say that it would undo the normal apply and
apply with a different mix, or something like that
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