I’d like to track and export “Time in Custom Field” at a task level. Right now, I’m able to successfully create a chart in a portfolio dashboard that displays average time that tasks spend in each option of a custom status field I’ve set up, using the “Time in Custom Field” functionality. However, I can’t click into the chart to view further or export it. Ideally, I’m able to view and export this at the task level.
Is there a workaround? The only thing I can think of is creating a rule that populates a separate, new “Status Changed On” field that fires when the value of the original field is changed. That would give me dwell time for existing status option (although, wouldn’t be able to easily backfill it).
Welcome to the community @Emily_Oates! 
Asana doesn’t currently support exporting the task-level breakdown directly from the portfolio dashboard chart itself. That chart is a rollup/summary view, so you generally can’t click into it to export a task-level history from the chart.
A practical workaround is to use a rule to stamp a separate “Status Changed On” (or similar) date field whenever the custom field changes, then pair that with a report/export structure that calculates dwell time from that change date and the current date. One caveat: this won’t backfill historical dwell time cleanly unless the change history was already being captured.
Depending on how you want to view the data, you may still need a separate field or reporting structure to make the export work cleanly.