You can use an exclusion list to specify the domains that View excludes from the results of a domain search. This will not only speed up your environment, but it will also be less confusing to end users that need to pick the correct domain to log into.
On your View Connection server, open an elevated command prompt and enter the following:
C:\vdmadmin -N -domains -list -active
This will show you the domains that are currently active and listed in a domain search for the View environment.
Now we want to remove any domains that we don’t want showing up. Type the following command:
vdmadmin -N -domains -search -domain BADDOMAIN -add
In that example, BADDOMAIN is the domain we want to remove from the listing. Repeat these steps to remove other domains. You will not be able to remove the primary domain associated with your Connection server.
More information can be found in the documentation here: https://pubs.vmware.com/horizon-view-60/topic/com.vmware.ICbase/PDF/horizon-view-60-administration.pdf