We use an article custom field named 'partner' managing an ID. Inside this article the code {article}[partner]{/article} displays the value. (369)
Using this ID to show the title of the article with ID = 369 we use the following code {article id="369"}[title]{/article}.
We now want to use the custom fields value (ID) dynamically inside a template system, maybe like "this:partner" -> {article id=this:partner}[title]{/article}.

Is there a way to realize this? Any ideas?

Thanks for your answer Peter. It's exactly what I tried. The custom field named "partner" is a "articleslinked" type field and as layout a custom html is defined. It's just [id]
So when using {article}[partner]{/article} it gives back the ID as expected.
When using this:partner like in your example it gives back 1 (probably the default value from the articleslinked field).

Last solution for us could be a more complex custom html layout with all field infos and html code inside.
Just using [id] would make the template system more modular and flexible.

But maybe there is another option for our case?

Hmmm, tried your and another approach (see below). But there are no values returned for both codes.

{article}{article-nested id="[partner]"}[title]{/article-nested}{/article}

{article id="{article-nested}[partner]{/article-nested}"}[title]{/article}

Joomla 4

Output of {article}[partner]{/article} is 369 (ID of linked article defined in custom HTML).

Output of {article}[partner:text]{/article} is 1 (default value of articleslinked custom field).

Thanks for your weekend work! Let me know, if there is a solution.
Maybe a complex custom html code is needed to solve this for now. 🙁

You are right, I just looked at the result.
The complete code output is

Yes, that's it.

I created an alternate layout for custom fields just outputting the value without the span tag, choose this as default layout in the articles linked custom field options. Using a custom HTML layout with outputting just [id] additionally is the solution for using different article fields of the linked article in a template system like Yootheme Pro.

THANK YOU!