I recently was looking to recover my Postman collections that I had saved locally on my macbook. I created a new user and wanted to copy my data over from my old user.
I saw this question asked for Windows, but struggled to find a current answer for mac.
I believe the collection data is saved in the IndexedDB directory in /Users/<username>/Library/Application\ Support/Postman/IndexedDB
I was able to restore all my Postman data and settings by deleting the /Users/<username>/Library/Application\ Support/Postman directory for my new user, and copying the old version of that directory, which included the DB of my collections.
I had a similar situation where I had a local workspace of collections. When I signed in to my account I lost all my local collections.
I navigated to /Users/<username>/Library/Application\ Support/Postman/
and there were a number of backups with the naming convention 'backup-yyyy-mm-ddThh-mm-ss' e.g backup-2021-06-30T15-02-29.
Importing this into my logged in account managed to salvage the majority of my local collections.
I'm on version 9.2.0 and if you go to Preferences->Data you see an Export Data button.
