So, I think users should be allowed to modify their own charts of accounts and delete whatever is not necessary to them!

Dear you really need to talk to an accountant. No user should be able to have their own chart of accounts. COA is a company wide agreed principle of accounting and users do not have their own.

As @apmuthu said..you as a system admin (with the help of  an accountant) can decide on which accounts you want to
keep or delete/add.
After that these accounts and once they have transactions against them will always show in reports for audit purposes but can be disabled for further input.

Opening balances must necessarily be entered as journals from your old balance sheet and / or by credit/debit notes.

So, I think users should be allowed to modify their own charts of accounts and delete whatever is not necessary to them!

I have noticed that an account cannot be deleted even if you remove all transactions linked to it... It still says, THE ACCOUNT CANNOT BE DELETED BECAUSE THERE ARE TRANSACTIONS DONE WITH IT!!!
Yet I have deleted all transactions with that specific account.

The only option i had was to login in the database and delete the record, but what about the end users, they have no access to the database, how will they delete accounts which the do not want anymore????