That is possible if the field in the pagestate is a dummy field. In the filter expression you can add an extra parent to get to any dummy field on the pagestate.
It does clear things out a bit for me and that tells me that most likely, what I am trying to achieve is not possible within the Architect.
A key part of the question is that the Filters plugin is involved. I know that it stores certain values as list of tuples in the page state (which is used in the JavaScript of the plugins using the Filters plugin). This is what I am trying to retrieve in the architect.
I think that indeed it will be difficult, if not impossible, to do this without using plug-ins. The ChartClickAction in the Charts plug-in contains an example of applying a filter to a grid based on the Filters plug-in.
Indeed that is what I thought. The question is now a feature request SR for the GridFilters plugin. Long story short, we want to introduce new type of grid, that in a sense does something similar to what the Charts or Timeline plugin do with the Filters plugin.
I consider your answer the Solution to this topic, so we can consider this closed.