In case you want to add more disk types in the dedicated pages of the theme, here is the detail process for the same.
Step 1: Login to your website directory via cPanel or FTP.
Step 2: Go to > your whmcs installation/modules/addons/hostx/
Step 3: Locate and open "languageHostX.php"
Step 4: You will see the code
Add a Disk Option in the code like this:
Now you can see that the new TEST disk type is added.