If you're using the Postman Chrome app,
1. We strongly suggest you move to the native apps (https://www.getpostman.com/apps) :). Chrome app has been deprecated (for OSX / Windows / Linux), and the native apps support a lot more features.
2. Before reinstalling, head to chrome://indexeddb-internals/ and search for "fhbjgbiflinjbdggehcddcbncdddomop". You should see two folders listed - you can backup the contents of these folders.
3. Reinstall (navigate to this link and reinstall the latest version) and move the backup to its original location.