How are you adding your parameters? The number of decimal places displayed is based on the interval of the NormalisableRange of your parameter e.g. an interval of 0.1 will display the parameters with 1 d.p.
Have you performed a before/after comparison? Before it would show -2.3dB for gain, now it shows something like 0.87034153. This is not just about the number of decimal places, that is just a symptom of the formatting (including scaling and adding the suffix) getting lost.
This happens independently of how I add the parameter. As soon as I add any formatting relevant information, it is ignored. And that is not only true for the generic editor but also for all things automation related.
I have not tried custom formatters, because before it worked without using them and they are only providing redundancy. My point is not that there is no workaround, there clearly is, but that there is a behavioural regression that should either be fixed or at the very least be documented and reasonably motivated.
Here is the most simple parameter construction that already shows the problem. It doesn’t have a suffix, but the scaling and formatting is messed up:
OK, this commit should revert the display behaviour to using 2 decimal places when the simple AudioParameterFloat constructor is used.
Can you clarify what you mean by the scaling and suffix formatting being affected? It would be useful if you could post some code which demonstrates the behaviour change. And also, just to be clear, when you say that this issue is present in “Logic’s generic parameter editor” do you mean the editor which I posted a screenshot of above which is displayed when you select the “Controls” view in the Logic AU editor window, or do you mean JUCE’s GenericAudioProcessorEditor?