Hi Kit,
I know exactly what you are going through. I had to make a really complicated workflow that had many different types of features. Some needed to be added as new feature, some needed to be updated at specific times based on other criteria and were indicated by symbology changes (this is not possible in Survey123 inbox, but works in Collector), and we had over 40 fields but they weren't always relevant, so we really benefited from the smart form abilities of Survey123. In short, we needed features from both Collector and Survey123. We used the Custom URL as suggested above, but with a little trick to make the final workflow less "clunky" for field users, but it adds a little more work on the data management side.
You CANNOT use a custom URL to open an existing record in Survey123 (unless they have added the feature in the past year), nor can you have a link to take you to Survey123 when you are adding a feature in Collector. You can only link to Survey123 when you open the popup of existing features. This is obviously a huge limitation that ESRI has failed to address, but we worked around it.
As I said, we really needed Survey123 for the smart form abilities so we collected all of our initial data in Survey123. A few fields needed to be edited on occasion, so I made this visible in the popup so they could quickly be edited in Collector without navigating through Survey123's inbox map. The caveat is I limited this to simple fields that would not require any smart form capabilities or conditional formatting.
For more complicated updates, I did need to use Survey123, but I wanted to be able to do it directly from Collector so I setup another Survey123 with the updatable fields. Users would click the feature in Collector and then follow a hyperlink to the new survey. The hyperlink would also pass the my own ID code (I used this instead of the recommended GUID because for some reason when I opened the data in ArcGIS pro it changed the case of the letters and broke the links.) to the new Survey. Then I used an arcade script, behind the scenes, to apply the changes from the new survey to the original survey. To the field workers the main drawbacks were they had to submit 2 surveys at the end of the day (we were working offline) and they had to swithc back and forth between Collector (to Navigate and update features) and Survey123 (strictly for adding new features).
It's a lot more work on the back end though. I wish ESRI would just make the inbox map more useful, or give us the ability to use conditional formatting and calculated fields in Collector . It would make the Apps so much more useful for complicated workflows. Currently, without some knowledge of programming, Survey 123 is only useful for initial collection and infrequent / basic updates, and Collector is useful for simple data schemes.
