4. Set your preferred hotkey.
5. Open a new window for the hotkey to work. Press the hotkey you set and a notification in the corner will appear.
Go to about:cache in Firefox to see cache usage before and after clearing cache.
Other Storage Policy:
STORE_ANYWHERE - cache stored in any device
STORE_IN_MEMORY - cache entry in non-persistent storage (RAM)
STORE_ON_DISK - cache entry in persistent storage (HDD)
STORE_ON_DISK_AS_DISK - cache entry in persistent storage in a specific file