Edit: Now also with functioning screenshots 
Hi! Sorry for the late reply!
so this is how it flows. we use one slate module for both directions.
From Object Set to Stringified Filter :
we pass this filtered object set of into slate named “modified-default-filter”
it gets passed and saved in slate as “v_modifiedDefaultFilterJSON”
Here is how the function looks:
The function outputs “f_modifiedDefaultFilterAsString”, that is sent back to workshop under the id “updated-default-filter-string”
Et violà! In workshop the stringified filter will look like this:
From Stringified Filter to Filter variable :
To go backwards we pass in the “saved-filter-string”
The stringified filter gets converted via this function and returned to workshop:
I hope this helps!