how to customize a Record type User Filter

Did you try to execute this logic in a separate expression to better understand what it is doing?

no basically,
I am trying to lower the options on this record user filter

Sure, but as the items you create the options from are coming from that query, you might first want to investigate that aggregation.

I can get the correct query.
is this one:
local!assignees:a!queryRecordType(
recordType: 'recordType!{4390cf3b-8f80-4bfd-adfa-b06cb2562f7d}Job Corps Response',
fields: {
a!aggregationFields(
groupings: a!grouping(
field: 'recordType!{4390cf3b-8f80-4bfd-adfa-b06cb2562f7d}Job Corps Response.fields.{assignee}assignee',
alias: "assignee"
)
)
},
filters: {
a!queryFilter(
field: 'recordType!{4390cf3b-8f80-4bfd-adfa-b06cb2562f7d}Job Corps Response.fields.{assmtFocusAreaAudId}assmtFocusAreaAudId',
operator: "in",
value: tointeger(
index(
local!assmtFocusAreaAuds,
"assmtFocusAreaAudId",
{}
)
)
),
a!queryFilter(
field: 'recordType!{4390cf3b-8f80-4bfd-adfa-b06cb2562f7d}Job Corps Response.fields.{compliantStatus}compliantStatus',
operator: "=",
value: "No"
),
a!queryFilter(
field: 'recordType!{4390cf3b-8f80-4bfd-adfa-b06cb2562f7d}Job Corps Response.fields.{stmtTypeId}stmtTypeId',
operator: "=",
value: cons!ROAP_INT_COMPLIANCE_STMT_STMT_TYPE
)
},
pagingInfo: a!pagingInfo(startIndex: 1, batchSize: 500)
).data,

as you can see I have a local variable call local!assmtFocusAreaAuds.
I have no idea how to set that up on the Record type User Filter

So, when that query returns the data exactly as you expect, then you can turn that into a user filter as you do in the code you posted above. Where are you stuck?

BTW:

yes,
I have the query that returns what I want:

a!queryRecordType(
    recordType: 'recordType!{4390cf3b-8f80-4bfd-adfa-b06cb2562f7d}Job Corps Response',
    fields: {
      a!aggregationFields(
        groupings: a!grouping(
          field: 'recordType!{4390cf3b-8f80-4bfd-adfa-b06cb2562f7d}Job Corps Response.fields.{assignee}assignee',
          alias: "assignee"
        )
      )
    },
    filters: {
      a!queryFilter(
        field: 'recordType!{4390cf3b-8f80-4bfd-adfa-b06cb2562f7d}Job Corps Response.fields.{assmtFocusAreaAudId}assmtFocusAreaAudId',
        operator: "in",
        value: tointeger(
          index(
            local!assmtFocusAreaAuds,
            "assmtFocusAreaAudId",
            {}
          )
        )
      ),
      a!queryFilter(
        field: 'recordType!{4390cf3b-8f80-4bfd-adfa-b06cb2562f7d}Job Corps Response.fields.{compliantStatus}compliantStatus',
        operator: "=",
        value: "No"
      ),
      a!queryFilter(
        field: 'recordType!{4390cf3b-8f80-4bfd-adfa-b06cb2562f7d}Job Corps Response.fields.{stmtTypeId}stmtTypeId',
        operator: "=",
        value: cons!ROAP_INT_COMPLIANCE_STMT_STMT_TYPE
      )
    },
    pagingInfo: a!pagingInfo(startIndex: 1, batchSize: 500)
  ).data

however I want to use the Record Type User Filter. 

I have no idea how to set up a variable that is going to change according to the record is being display. Am I force to only use a Costume Filter?

I have a hard time trying to understand what you try to achieve.

What exactly do you mean with "change according to the record is being display"?

But maybe the answer is more simple, as user filters do not support any way to react on the data being displayed.

I have a hard time trying to understand what you try to achieve.

What exactly do you mean with "change according to the record is being display"?

But maybe the answer is more simple, as user filters do not support any way to react on the data being displayed.

so as you can see in the grid below. There is only two items on the entire grid. 

But look at the options for the GRID Filter. There are over 50

Hi sergiog132707 
The reason why its showing over 50 records is because you are using assignee user filter of another record. 
In order to show only those 2 assignees, you have to aggregate based on the grid which is being displayed in findings summary page. I am assuming its coming from a different record. You can create a user filter in that record and it will show it up here