Is it possible to add the RSForm titel {global:formtitle} in the email send to the admin (Admin Emails)?

Did you find a solution for this?

In the php code of the extension I find {global:formtitle}, so I suppose you can use it. It hasn't been added to the toggle list with placeholders, but you can try if it works.
If not, you can create a hidden field and use this value in your email.

Hello,

The Global Placeholders available for RSForm!Pro are listed here. The form title is a static information, thus there is no actual need for a placeholder since it can be manually written.

You can however try adding a hidden field in your form and add the {global:formtitle} placeholder in its Default Value area. Afterwards, use the hidden field's placeholder within your email message, for example:

{my-hidden-field:value}