and your #3: EXIF tags are standard: recorded into standard datablock (EXIF IFD for TIFF-based files, APP-blocks for JPEG based, separate data block for MP4-based), uses standard tag values/types, everything is described in public standard.
Most of EXIF/standard tags are covered by FastRawViewer EXIF display tune dialog. We're open to additions to this dialog if we've missed something useful.
Makernotes tags are a) not always recorded in TIFF-IFD-style tags b) not described in any public/official documents, but guessed by community with unknown quality c) usually requires vendor/block format specific code to parse.
So it is just not possible to create 'configuration file' that will allow user to add own Makernotes fields to display: this will require some underlying code to parse vendor-specific non-standard data.
A) FastRawViewer displays dc
A) FastRawViewer displays dc:title/dc:description XMP tags (you may need to check Display Title/Display Description in XMP Metadata panel gear menu)
B) FastRawViewer is able to run external program via shortcut (menu, context menu), to configure your prefered programs use Preferences - External Editors https://updates.fastrawviewer.com/data/FastRawViewer2-Manual-ENG.pdf#pag...
and your #3: EXIF tags are standard: recorded into standard datablock (EXIF IFD for TIFF-based files, APP-blocks for JPEG based, separate data block for MP4-based), uses standard tag values/types, everything is described in public standard.
Most of EXIF/standard tags are covered by FastRawViewer EXIF display tune dialog. We're open to additions to this dialog if we've missed something useful.
Makernotes tags are a) not always recorded in TIFF-IFD-style tags b) not described in any public/official documents, but guessed by community with unknown quality c) usually requires vendor/block format specific code to parse.
So it is just not possible to create 'configuration file' that will allow user to add own Makernotes fields to display: this will require some underlying code to parse vendor-specific non-standard data.
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Alex Tutubalin/FastRawViewer team