I have wanted this as well as I have a similar situation. I have a sheet with Lessons that are taught to students. In another sheet I have billing cycles where a coach can select a date range for billing of their students. Through formulas in the sheet, each lesson is assigned to a billing cycle. Then in a third sheet I use a query to get the unique Student/Coach/DateRange combination. This way, through relations, I can display only the student’s lessons that were taught by the signed in coach within the date range they selected. I my case I have several other columns doing calculations in the sheet and also incorporate payments for each billing cycle, so I’m satisfied with using a query.
A grouping or unique option would be nice, but I suppose in most cases a list in glide needs to relate to an actual row in the sheet Grouping wouldn’t allow you to do this and the only option would be to display a list with no action (like how you mentioned that charts work). Long story short, I don’t think it’s possible with the current glide only functions?