- If you have too many kinds of bands (more than 5 by default), a group with average values appears. If you then press Apply without changing values, all the bands in that group are changed.
- The interface allows that you enable/disable or delete bands while the dialog is open. If you then press Apply, planet earth is obliterated.

2nd attempt to enter this
- merge checkboxes
- logical ordering among flocks with equal number of bands

Added OK button in place of the no longer needed Close button

* Indexed search to allow serious amounts of bands without delay (tried with 500+ bands).
* Removed length from grouping criterion, except that zero-length bands are treated separately from non-zero length. No length slider appears for zero-length bands (which means you can' make them non-zero length in this GUI, but that seemed useless). Strength can be set more accurately if strength <2, and less accurately but more easily if strength >= 2. So to make a < 2 strength bunch stronger than 2, you have to max out at 2, apply, and then move on.
* Recipe output window shows what changed.
* Merging in a separate dialog, to unclutter the main window and allow more control.

Fixed fatal bug at startup if bands longer than 20 exist (recipes like comperssor can do that) and better handling of the length sliders.
Set strength to -0.01 to delete bunches. Strength < 0 is not allowed. I don't notice that strength 0 is any different from disabled but there's no harm in keeping the option open.

Now the slider kept its maximum value of 2 out of reach; and rounding down of strength occurred again. Reduced the span of the slider and added a boost checkbox, which covers the previous implementations and is a quick way to max out a default strength of 1.

O dear, o dear... r7 was a thoroughly amateur implementation of deletion, not considering that band indices change.

For Pete's sake, enabling wasn't working anymore either.

After multiple experiments, settled on a single, lower precision scale for strength.
Better handling of rounding: sliders not touched should not provoke a change.
Much more terse output.