I’m having issues when don’t realise I have not enough funds in euro currency. The application automatically takes it from other currency. If you provide a way to lock certain amount of balance it would damage can be avoided especially white cryptocurriences where I lose.
Also I never top up a large amount because this is not a credit card in case of fraud there is no assurance the money can be returned.
If you provide a way to lock amounts im happy to keep large amounts on the account.