Is there a way to delete all transactions by a single click or can I export chart of accounts to a new company?
No. But you can do Batch Deletes on bank and cash transactions. But that leaves all your invoices, credit/debit notes, transfers, and other things. It would be faster to build a new chart of accounts that try to cancel everything in an old business.
am i missing something here? i do not see a batch delete function in my installed copy of Manager.
just for your info.
You can only do 
on bank accounts not cash accounts as far as I am aware.
Click on the Bank Accounts tab, click on the bank account’s blue figure balance and then scroll to the bottom right corner.
yes. thank you. i was just looking directly in the Bank Accounts and Bank Transactions tab. so obviously i did not find it.
Creating A business template with pre defined set of Chart of Account is the optimal way. You can also create for different industries. So you can always import the copy of business template data entered the necessary information without putting your time on pre defined coa. Applicable to other Bank Account, Cash Account, Supplier, Customer Listings. Since there is no limit how many files you can create and import into manager software. The only time consuming is updating the template but less frequent to do so.