Anaplan report pages and module saved views as data source
As I was working with Anaplan new report page I noticed that there is no possibility to use module saved views as data source for these report pages. (I have also added some picture for references, please check 1st picture for this case). Pages and worksheets offer this functionality and I think this is a very crucial feature needed for reporting, because it allows you to hide and filter data that is not needed for your page (check 2nd picture).
Right now if you want to hide something from your data source in report page, you need to select items to hide/show them for all rows or columns in a data source. However in some cases you need to hide some items in rows or columns, because they are not needed. As I mentioned previously, module saved views solve this problem, however they are not available for new report page in Anaplan.
I understand that not being able to use Saved Views can be frustrating, but you can still use Custom Views for your purpose - on the screenshot below I highlighted icons that open menus for Filtering and Selecting.
However, I don't understand your second paragraph - do you mean that you want to apply selection to nested dimensions (so more than one dimension in rows/columns)? If so, you are right - it cannot be done in New UX Custom Views, but I believe It's also something that Anaplan don't want to allow on Management Reports - grids here shouldn't be big or complicated.
In second paragraph, I described hiding and showing specific items just like when you do it in Anaplan modules once you click on item and hide it. Right now, new report page in Anaplan only allows to hide or show items by selection, which means that if there is a nested dimension, you can't select items to hide from specific rows or columns.