TwentyX is a WHMCS 8.3 Child Theme, due to which the changes you will make in your client area using this, will not lose after theme or WHMCS updation. Customizations will be compatible with the latest version of WHMCS.
https://whmcsglobalservices.co....m/clientarea-templat

TwentyX WHMCS Theme: Uniquely Crafted Child Theme - 20% Off
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TwentyX WHMCS Theme: Uniquely Crafted Child Theme - 20% Off

Use TwentyX with the WHMCS 8.6 Twenty-One Theme to make your client area fast, attractive, and easy for your clients.