Describe your feature request

I would like having a setting for custom export tasks that call a user-provided pandoc command, instead of using the export menu.

What problem does this feature solve? [optional]

• Allows to export to pandoc-supported formats without adding specific menu items
• Allows to reuse custom pandoc export commands used in other contexts
• Allows specifying a pdf engine in pandoc in case the default one causes problems

Additional context [optional]

• Abricotine does this by the way of having a "tasks" array in their settings.json file in which one can specify tasks with a given title and command, with %inputFilepath% and %outputFilepath% as variables that get replaced with the input and output filenames