Both the Polkadot browser extension and Polkadot-JS UI only show your mnemonic phrase once: during the initial creation of your account. 


If you miss taking note of it, or if you misplaced your mnemonic phrase, there is no way to view it again at a later stage. While you can always restore your account from your JSON file, you won't be able to see your mnemonic phrase again. For this reason, it is very important to save it in a safe place (preferably on paper) at the time of account creation. You can learn more about storing your mnemonic phrase here.


‼️ IMPORTANT

The Polkadot extension is an account manager meant for power users and developers. There are several user-friendly browser extensions funded by the Polkadot Treasury that support a lot of features right from the extension. Discover them on Polkadot's homepage.


The only workaround for this would be to send your DOT to a newly created account:


1. Create a new Polkadot account.


2. Take note of the mnemonic phrase and save your new JSON file in a safe and secure place.

3. Send all of your funds from your current account to the new one.