It all depends on what type/format of data you're trying to exchange and how you want to exchange it.  Is it HL7,  SWIFT, custom format...? Will it be via a file, email, TCP/IP, FTP...?  There are adapters available in Health Connect to use in services and operations that will handle a wide variety of types and protocols.  Have you taken a look at the online materials in the InterSystems Learning Portal?  There's a resource guide Learn Ensemble for Developers and System Integrators (Ensemble was the precursor to Health Connect) that may be helpful when first starting out.  It has a lot of information about how to design and build integrations.

If you provide a little more about what you're trying to do, it'll help in being able to provide more specific guidance.

The e with an accent is easily typed (on a Windows laptop) by holding down the ALT key and then 0233 - é.  It's little effort to make it clear in distinguishing between the two terms and I wish more people would do it!

Disclaimer - Mac results may vary

I haven't coded DTLs for quite some time, but recall that I used code actions in a few places to set/use local variables, for example, to help keep track of the number of occurrences of lines in blocks of NTE or OBX segments in result messages.  One scenario I recall is where a lab system wasn't sending comments in the right place for the receiving system (since in an ORU_R01 message, NTEs can exist after the PID, OBR or OBX segments) and so we needed to move/copy the notes somewhere else in the msg. Undoubtedly, this could have been handled by a custom function, but sometimes developers just do things the way they know how to, and not necessarily the 'best' way!

The team would also use code actions quite often to insert comments into DTLs to help explain or document particular processing etc.