Context: Discussion at https://confluence.camunda.com/display/CO/2021-01-28+Dashboard+Filter+Application+Followup
OPT-4815 we change the default behavior of variable dashboard filters so that they apply to all process reports on the dashboard, no matter if the underlying process definition contains the variable or not. We might want to give the user the option to customize this behavior.
Currently, Dashboard Filters are always applied on top of existing report filters and combined with AND. E.g. if the Report already has a filter "assignee = A" and the user adds a dashboard filter "assignee = B", only instances with "assignee = A AND assignee = B" are returned. We might want to give the user the option to alternatively combine the filters with OR, so instances with "assignee = A OR B" would be returned.