Note that you can just open another instance of OpenMPT and load the module there, and then copy&paste the parameter values.

I don't see much merit in a function that can just restore the plugin state from the time the module was opened, because then the next person wants the same function but with the state five minutes after the module was opened, etc.... you see where this is going - we would need to have a full undo system for plugins, which would be nice but probably not very feasible since it is not uncommon for plugins to have 1) huge state 2) long save times for said state. If we were going to record every parameter change, this would result in several MB of data per second for some plugins (e.g. Korg Wavestation, where a single undo point would be roughly 500KB).

You could just save the plugin states as fxp presets whenever you get the sound you're happy with. Not only you can use it to restore the previous state, but you can easily import them when making another song.

That argument is on the same level as "you could save your sample everytime you like it, you don't need undo in the sample editor" though. Sometimes you just don't know yet that you will want to revert to a certain state later. But in the case of wanting to return to the status of the last save, you technically already save an FXP file, but it's embedded in the module file. ;)

Actually that's a nice workaround. I didn't even think about that! Even better, i can save the program with its parameter edits in the second instance, then reload in the first.

And your argument about WHEN a restore point is saved based on user preference is unjustified. In discussions with other users of other software that does have a Revert command, no one has ever mentioned that they wished they could revert to a state of the program or settings after the initial state. That argument seems contrived and specious. Nor was i asking for an Undo slate for plugin edits. Even I myself know that's a bit much. ;)

Still, i liked your workaround and think that should be inserted somewhere in the Plugins section of the manual, in case someone needs to do that in the future. Consider the matter closed/resolved...8)

That argument seems contrived and specious.

It's not contrieved, because that is precisely what "Undo" does - reverting the document to any previous state the user wishes to go to. On the other hand, having a special "revert to original state" command just for plugins would be inconsistent with the rest of the software (and is redundant with opening the file in a second instance, as mentioned before).

Still, i liked your workaround and think that should be inserted somewhere in the Plugins section of the manual, in case someone needs to do that in the future.

Once again, being able to open two instances to look at the original state of the module is not specific to plugins, it can be done for any other property of the file as well and is not a special feature of OpenMPT, so I don't see the point in documenting it.

Anyway, I will keep this request open and rename it, to have an issue for tracking undo for plugin parameters.