This is 3 of 3 in a series of feature questions. (1 2)
I probably asked a version of this question some years ago but can't find it, and probably didn't express it properly then.
Would it be possible to output a Diff showing changes between standard Prefs and current Prefs?
Thinking it could be helpful for troubleshooting.
Even if there's no GUI way now, if someone could point to a couple of files we could diff, that could be helpful.
It depends which preferences settings you change. I usually compare the whole /dopusdata to a previous copy and drill down from there.
Yeah, I usually diff my 'golden' Opus Config Backup (after extracting as a zip file) to my current /dopusdata folder in order to sniff out what changes I've made recently that I may or may not want to keep (and commit to a new 'golden' config backup).
I don't generally do an actual comparison against 'standard/default' settings though... since doing so would just reveal such a MASSIVE amount of changes in the case of my own customizations 
, and casually finding anything specific falls victim to the needle-in-a-haystack effect. I do however keep a copy of the default settings from each Opus version and often role back to those defaults in order to test if an issue I bump into is reproducible with the default settings or not.
Note: there was another thread recently debating the merits of keeping a default OCB, vs deleting the /dopusdata folder, vs uninstalling and then reinstalling in order to get yourself back to default settings. Personally, I'm aware of the trade-offs and find restoring a backup of the defaults of the 'same version' I'm currently running works out fine. But then again, I'm not among those who get twisted at the prospect of uninstalling/reinstalling and a few reboots in order to maintain my copies of default settings backups for new versions...
Also, worth mentioning that comparing the actual config files like Leo and I mentioned is probably not a beginners task . You're usually looking at raw XML and may see LOTS of diffs depending on what's been changed from the defaults - much of which may not be all that intelligible without doing some experimenting. Particularly settings that are stored as FLAGS of various top level options. So the value of doing comparisons of config files really depends on what you're trying to figure out. If it's really for troubleshooting purposes after discovering a problem, Leo mentioned in the thread that I linked to above that many individual parts of Opus can be reset to defaults - such as individual Prefs pages, from the Prefs dialog File menu.
Yeah, echoing what Steje says, diffing a config is usually only useful if you made a backup of it very recently. I sometimes do that before I start changing things, so I can then check exactly what was changed (or ensure I'm back to exactly how things were, if the changes were only meant to be temporary).
Sometimes it's also useful if someone has a problem and I want to look for differences between their config and my own or the default, but that's not something most people will need to do.
Much thanks for your insights, guys.
As you're saying, it sounds like with basic diff tools this is not an operation one would want to do everyday.
Generally yes. But... again, I think it depends on what you're trying to do:
Troubleshooting: I don't think THIS goal is best served by comparing raw config files - IF you are in fact inclined to test and/or compare between the 'default' settings and your 'current' config. If you've encountered an issue and want to test if it might be related to a non-default settings change you've made, you might have a place to start that could direct you to a specific Prefs settings that you could reset from the file menu. In that case, for a single prefs page - you might be better off just visually comparing screenshots of the settings on that one page. If not, you could go deeper and use one of the techniques mentioned to roll back to default settings altogether - and retest the problem. If doing this DOES circumvent the problem, at some point you'll still need to narrow things down to at least one Prefs page - so maybe you reset page-by-page from your normal custom config.
That said - I WOULD however say that if you know ~something was working at some point and you suspect it broke as a result of subsequent changes, then I can say comparing a 'golden' config backup from a few months ago to your current settings probably isn't too burdensome - subject to how many changes you've made between then and now of course. Also, for people who don't make HEAPS of customizations from the defaults, maybe doign a raw compare of defaults vs current isn't too bad either. But... we're ALL customizing the hell out of Opus... aren't we ???
Configuration Management: I do this ALL THE TIME, usually between my most recent 'golden' config backup and my 'current' config. And I do this mainly because at any given time I have a combination of new customizations that I WANT to keep and carry forward into an updated 'golden' config backup - along with some temporary things (either from experimenting, or for the purpose of trying something out to help someone on the forums) that I do NOT want to keep. Having some of each means I'd capture unwanted 'temporary' config changes if I were to simply export a new config backup using the built-in Backup & Restore tool. In this case, I do it often enough where the differences to sniff out in the raw config files aren't so burdensome compared to diffing the 'defaults' against my 'current' config since soooooo much is different...
@steje Fascinating. Sounds like you're the master of configurations. You're motivating me to dip my toes into prefs diffing.