I work for a company that does a lot of field inspections, and one of the Achilles heels of AGOL/WebApp Builder "out of the box" has been that inspection records in a related table must be added individually. Or they can be added en masse to a related table by a relatively cumbersome process of exporting a table of inspections to be completed, editing that table, and then appending that table to the live feature service (not much of a time saver).
What I would LOVE to see is a widget in WAB that, similar to the batch attribute editor, allowed you to ADD a related record to multiple features in one fell swoop. In other words, if a hydrant flushing crew flushed 100 hydrants this week, it would be fantastic to be able to highlight those 100 hydrants, and then add a related maintenance record (with identical field values) to each with a few clicks that denotes they were flushed, without having to visit each point and add the same related data to each. I'd be happy to hear someone say this functionality already exists and I've just missed it somewhere in the last update cycle (PLEASE!), but I'm pretty sure it doesn't.
I'm not a programmer (enough python and SQL to be dangerous to myself and others), and we don't run server (I'm sure this is fairly common in the community). I'm sure there's a way to program your way out of this issue with database triggers and custom widgets, but it's probably out of my and many others league(s) for right now. I think this would be a VERY popular widget in the field-data collection and management community, so any info on plans for such a thing would be appreciated.