how to customise the de_de.notify_template.html

Hello,

we have installed SuiteCRM on our server to handle customer requests, which means to assign them to a specific contact person.
In this context of course notification e-mails get submitted and forwarded to the assigned contact.

But how can one configure this email-template? Out of the box there are three fields:
Name: {LEAD_NAME}
Lead Source: {LEAD_SOURCE}
Status: {LEAD_STATUS}

But how can fileds be added? This would be essential for us because the salesman, who are going to get the requests need the complete contact data of the customers within the notification mail!

I tried a lot, which you can see here as an example, but the notification mail never contains the corresponding values:
Name: {LEAD_NAME}
Lead Source: {LEAD_SOURCE}
Status: {LEAD_STATUS}
Description: {LEAD_DESCRIPTION}
Description: {ACCOUNT_NAME}
Description: {LEAD_ACCOUNT_NAME}
Test: {LIST_ACCOUNT_NAME}

All the threads I found here regading this issue never got answered finally.

Thanks in advance for your help.
Thorsten