Variable: org-agenda-filter-preset
org-agenda-filter-preset is an alias for org-agenda-tag-filter-preset,
defined in org-agenda.el.gz.
Value
nil
Documentation
A preset of the tags filter used for secondary agenda filtering.
This must be a list of strings, each string must be a single tag preceded by "+" or "-". This variable should not be set directly, but agenda custom commands can bind it in the options section. The preset filter is a global property of the entire agenda view. In a block agenda, it will not work reliably to define a filter for one of the individual blocks. You need to set it in the global options and expect it to be applied to the entire view.