Bought and sold a coin a bunch of times and now it has zero holdings? Don't delete it!
Removing the coin from the portfolio essentially means that those transactions were never added. Any linked transactions i.e. entries created due to the 'add to ...' or 'deduct to ..' option will also be deleted i.e. it will affect other coins. The deletion will be irreversible!
Instead you can hide coins with zero or very small balances.