Remember added custom token details across accounts

[leafcutterant]

What problem are you trying to solve?
When I add a token to one of my accounts (addresses in my den) that MM doesn't support out-of-the-box, I need to mine the data from Etherscan. I need to do this again whenever I switch to a new account and want to use the same token.

Describe the solution you'd like
Once a custom token is added to an account, store its details locally and treat it as an out-of-the-box supported token for all other accounts. If this is not possible, at least make it addable through searching for the symbol.