Syntax for a .join('\n') in a Flow

I have this code I use outside of a flow:

booking_form_links.setValue(search_activities.data.search_activities.values(`title_internal`).join('\n'))

I want to replicate this code inside of a flow.

However, the Wappler user interface doesn’t present me with the Collections menu from where to choose the .join(). So I’ve just added this to the code created by the flow editor myself, but it gives a syntax error for the .join('\n') part.

What syntax should I have in the join to make this work in a Flow?