Hello! In v16.8 which we are currently running, all the attributes added to Attribute Matrix don't have that checkbox for Show in Grid. I just confirmed that it is available in v17.0 but I tested it and checking or unchecking it doesn't do anything when viewing the Matrix Template where is it used.

Columns 2-4 are all Show in Grid checked except for Column 1. Viewing the Matrix Template that I added as a Content Channel Item Attribute, I was expecting that Column 1 Attribute will not show up in the grid. But there it is, still showing:

Anyhow, I'm exploring Content Channel Item as the channel that I can use for our web pages rather than using the Page itself with a bunch of HTML Blocks where the user has to learn HTML and CSS to edit and modify the  look and feel. So, with Content Channel Item, I want to utilize the Attribute Matrix Template using attributes to create a section layout in a page but the number of attribute just grew and with more than 10 columns matrix while viewing it makes it too busy and complicated like so:

I don't really need to see all of the columns (attribute) while looking at it, in this case, I only need the Content column so I know what it is and the last 2 columns. This is where the "Show in Grid" checkbox will be useful, it is to hide the attribute from being listed in the grid. I hid the unnecessary columns via CSS, but it would be nice to have that as an option while creating the attribute.