Newbie Simple D and Views question about grouping and "exclude from display" First time Views project simple question about Views and a HTML list of nodes with Taxonomy term. 

I have a basic list of nodes with shared taxonomy terms. The page displays all the nodes and taxonomy terms. When I add a group (under Style: HTML List), I see a new page element added duplicating the taxonomy term. Then, under fields is a checkbox, "Exclude from display" which has a description to suggest this fixes the duplicates when using groups. 

Now all the data is excluded! None of the other Field items has this Exclude checked. Each time I made these updates the changes were made immediately. Still, I cleared the cache before posting this missive. Why is all my node data missing from the page with this one use of Exclude? Is this a bug?
What was the problem? After adding "Grouping", I mistakenly thought Filter might contain the Exclude solution. I added it. Then, I recall, clicking Remove, but evidently I did not, or whatever.

Next, I found the correct setting: "Fields: Exclude from display", and then saved. But, what I saw on my end-user page (not preview) between changes was, 1) Grouping take effect, 2) Filter do nothing, 3) Exclude make a "blank page". I'm thinking there are some changes which take effect on the end-user page right away and other that do not. 

I'm going to try a new Views Development Workflow: 1) Export often, 2) Use save between each change, 3) Roll Back when things get weird. Repeat. And use the Preview instead of looking at my end-user page.