[sirinsidiator]

You need to define the function FilterScrollList and actually apply your master list to the scroll data.

function CharacterList:FilterScrollList()
    local scrollData = ZO_ScrollList_GetDataList(self.list)
    ZO_ClearNumericallyIndexedTable(scrollData)
 
    for i = 1, #self.masterList do
        scrollData[#scrollData + 1] = ZO_ScrollList_CreateDataEntry(1, { name = self.masterList[i] })
    end
end

In your case it would be better to change the content of the master list so you do not have to create the data entry all the time, since characters do not change during a session anyways.

for i = 1, GetNumCharacters() do
        table.insert(self.masterList, ZO_ScrollList_CreateDataEntry(1, { name = zo_strformat("<<1>>", GetCharacterInfo(i)) }))
    end

Then you can just copy the master list:

function CharacterList:FilterScrollList()
    local scrollData = ZO_ScrollList_GetDataList(self.list)
    ZO_ClearNumericallyIndexedTable(scrollData)
    ZO_ShallowTableCopy(scrollData, self.masterList)
end

In addition you can also overwrite the SortScrollList function to change the sort order of your scroll list.

function CharacterList:SortScrollList()
    local scrollData = ZO_ScrollList_GetDataList(self.list)
    table.sort(scrollData, myComparisonFunction)
end