When having configured a Multi-Add column in an SFM screen, single adding without using Multi-Add Lookup for that detail is no longer possible. There should be a possibility to add lines without using Multi-Add as well, as it was working in classic.
What is the underlying problem do you intend to solve with this idea?
Being able to use different sources to retrieve data from, when adding details
How is the problem being addressed today, if at all?
In Lightning the only workaround would be to dismiss Multi-Add and only use plain adding of rows