As an dashboard user, I want to be able to show all when editing a quick filter.
If you have a quick filter applied to a list formatted line item, currently if you try to edit that quick filter the drop down will no longer include items that were filtered out. This means that those items can not be quickly added back in. The whole filter needs removing and setting up again.
In the example below, I have a list formatted line item 1 dimensioned by time

Here, I have applied a quick filter to only show values of A for the line item 1. When I go to edit this quick filter, I am unable to then include other values as they are now omitted for the drop down.

The benefit of including a 'Show All' button here would be that it allows users to quickly filter items back in and prevent them having to remove and re-apply the filter, saving time and frustration.