Delphi - TNetHTTPClient - CustomHeaders

Question

I try create a wrapper for HTTP calls as a Dynamic Library and I have come this far I am able to add Header and PostData, however, I need to add some special headers which look like this:

NetHTTPClient1.CustomHeaders['HeaderName1[HeaderName2]'] := 'HeaderValue';

I use this to add "regular" headers

NetHTTPClient1.CustomHeaders['HeaderName1'] := 'HeaderValue';

I use Delphi 10.4 CE on Windows 10 Pro x64...

Any thoughts / ideas / solutions are really appreciated .....