Can users with the right permissions in a client$-$paid subscription add QuickBooks Online Payroll or QuickBooks Time to their QuickBooks Online company?

No$.$ Only accountants from QuickBooks Online Accountants can add additional subscriptions to client companies

No$.$ For new QuickBooks Online products, $$ey need to contact QuickBooks Online support

Yes, by going to the Billing & subscription section in Account and Settings

Yes, by selecting $+$ New and then Subscriptions