The easiest way to have persistent default printer redirection is to assign the Universal Printer as the default printer.

If your computers are part of an Active Directory Domain, you can also use Group Policy to set default printers. This functionality happens outside the TSplus Remote Access environment. Please see Microsoft technical document for more details.

You can also assign a full RDP desktop to the users, then set each user a default printer manually. 

Then switch back to the Floating Panel and the settings are remembered.