Digital Light & Color

If a transformation's dialog box is displayed, toggling that transformation's bypass button no longer toggles the passing of that transformation's change (or no change) downstream. Transformations from earlier in the branch are passed through OK, and they toggle as expected. The bypass button works as expected when the open transformation dialog is then closed. Have I missed some button or setting somewhere?

When a dialog box is open, calculation only passes through when you click OK or Apply.

The following behavior is not what I expect.
In a branch consisting of open file, then a brightness transformation, and then a color curve transformation, open the brightness curve dialog box, then left click on the color curve thumbnail to display the final image of the branch. This hides the brightness curve dialog box as expected. Now, right clicking on the bypass circle of the brightness curve thumbnail does not toggle the effect of the brightness transformation on the final thumbnail or the displayed image. This behavior is independent of whether or not the apply button was chosen while the brightness curve was visible. At this point one has a normal looking branch, but its behavior is not normal since the effect of toggling this transformation is not passed down the branch. It would be helpful if either the brightness dialog box did not disappear or the brightness transformation thumbnail were be marked in some way to indicate that its transformation will not toggle.

Point taken -- the only other workable alternative I can think of is the force the currently open dialog box to be closed when switching to a different image. This potentially has a lot of overhead in terms of propagating all the changes through the rest of the branch and it also overwrites the previous settings so you can no longer recover them by canceling. I would also probably have to add a confirmation dialog box to warn the user that switching to another image will close the current one. Still this may well be the right thing to do.

My original idea was to allow multiple dialog boxes to be open at the same time so you could adjust their settings and watch the results, but in the end I concluded the proliferation of windows would be totally confusing. Marking the thumbnail as open is a possibility, but probably also confusing.

My difficulties would be addressed if a transformation's dialog box did not close or become hidden if I chose to display another thumbnail's image. Don't hide them, and leave it to me to close the dialog boxes. They seem to reopen just as fast as when they are unhidden.
It would be nicer if changes always rippled down the branch rather than requiring the Apply button. The time and computational cost of automatic rippling would be irrelevant if recalculation further down the branch is halted the moment I make a change to the dialog box generating the current ripple. If changes always rippled, I wouldn't need the Apply button.
No longer hiding dialog boxes would eliminate another problem. If a hidden dialog box's Auto Preview has been depressed, changes from above will ripple to and through the thumbnail with the hidden dialog box. The changes do not reach this thumbnail or beyond if the button has not been depressed. That is, changes ripple as expected when a dialog box has been closed, but not necessarily so when a dialog box is hidden.

I tried leaving dialog boxes open initially, but the results were very confusing. For example, if you have two Multi Color Balance transformations open and each of them has color pickers open, since the color pickers have the same names, it is almost impossible to keep everything straight. With more than two or three dialog boxes open, the screen turns into a confusing mess.

If there were no Apply button, the program would become unbearably slow since every change you made would not only update the preview but also all the other transformations in the branch that depend on it. If you work with large images or with a slow computer, this is a big issue. Conflating Auto Preview with recalc propagation does not sound like a good idea either as there would be no way to preview without propagating changes.

I think the best solution is to ask to close (with an option of either Cancel or OK) the current dialog box when you switch to another. That way there would never be any hidden open dialog boxes to mysteriously stop the propagation of updates, and you would still have control over propagation of the current dialog box via the Apply button.

This sounds good.
With this change it seems like it will then be possible, for example, to display the final image of a branch (and have it update) while adjusting a transformation several images earlier in the branch.