Apply custom filter on Add Existing on Subgrid using Xrm.Utility.LookupObjects

Hello everyone,

I have been reading multiple blogs and posts regarding how to do this, but mainly, I followed this one:

https://www.magnetismsolutions.com/blog/paulnieuwelaar/2018/05/17/filter-n-n-add-existing-lookup-dynamics-365-v9-supported-code

I followed all the steps, but I cannot display the results of the filter. I am using the Unified Interface, and when I click the add existing button from the subgrid, I open the lookup control: https://docs.microsoft.com/en-us/dynamics365/customer-engagement/developer/clientapi/reference/xrm-utility/lookupobjects

I have disabled the MRU, so the most recent used records are not shown, but nothing is shown when I open the lookup control

and then if I click on search for more records, then all the records appears instead apply my custom filter.

Anybody knows how can I display the results of the pre-filtering in the lookup control from the add existing in the subgrid in the Unified Interface? 

Thanks in advance!