Multiselect optionsets are currently not supported in the Global filter (in UCI). Our users need the ability to filter the data based on the values of the multiselect option sets. The current workaround is to create a new boolean attribute instead of each value in the optionset, but this is not acceptable because there could be many values and it is impossible to add so many fields on the form, because it would be too big. Also, the maintenance is much easier when using the multiselect optionset.