I added the option in the xml file
1. Where is the COM_JDIDEALGATEWAY_IDEAL_EMS defined ?
2. How do I kink this option to a form ?
3. I updated the profile.xml file and it was overwritten somehow not
by me and erased the changed. Any idea ?
I tried to find in the documentation hpow to do it.
I looked for libraries with the name of the options
Language strings are located in the language files. This is located in source/administrator/components/com_jdidealgateway/language/en-GB/en-GB.com_jdidealgateway.ini for the back-end and components/com_jdidealgateway/language/en-GB/en-GB.com_jdidealgateway.ini for the front-end.
I do not understand the second question. The payment options will be shown when you edit a profile. Do note, you also need a paymesrv.xml file. You can see the other like ems.xml in the same folder as the profile.xml. You can copy one and adjust it to your needs.
The only way I can see this happen is if you updated RO Payments, that will override that file. While you are in development, it is best not to update the extension.