How to load an exported sidecar file

Duplicates are peculiar to Darktable, at least in my case, so I’m still contemplating how to take advantage of that feature. However, sidecar files are used in all of the other software I’ve used for developing raw files (i.e., Canon DPP4, Rawtherapee, ART). Canon allows for updating the raw file to include such data. However, I’m a fan of non-destructive editing and make a point of NOT doing that and rather use the options of creating a separate sidecar file instead.

At present it looks to me like the Duplicate feature of Darktable is nice for when you can plan ahead. However, the case I had in mind, that triggered this post, is the one where you produced what you thought was a final result, possibly long ago, and the processing for an image is done. Then for some unexpected/unplanned reason you decide to try something else on that previously (as in yesterday or a year or more ago) developed raw file. Having the sidecar file is an approach that works for all that other software. I’m inclined to think that generally speaking you cannot count on the sidecar file produced by an old version of the software to work properly with the version presently being used. My solution to that problem is to keep all of the old versions of the software which allows for also using such a sidecar file with the proper version of the program. This gets into a different post I made on this forum advocating for running such software in portable fashion. The only reason for bringing that up now is that I’ve also figured out that Darktable is NOT amenable to that type of installation. The problem appears, to me, to be the use of SQL Databases that must update in real time. USB portable drives are typically much slower at writing than reading data and when I did this the performance degradation of Darktable was so bad as to render it unusable. This is another problem that I’m still working on but thought it better to learn how to use it before worrying about how to install it. For now I am using a conventional installation. Anyway the idea of putting release dependent data in my work product is an anathema to me.