Search query grayed out on in-place hold settings

If you are a domain admin and exchange admin and tried to setup in-place hold setting, you might find the "search query" option is grayed out! You might think "oh no maybe it is the search engine!"
No it is not, you must be a member of "discovery management" group, add your account to be a member of the group, log out form the ECP and log back-in, try to create the in-place hold.

Ok now you done playing with in-place hold and try to delete the in-place hold, and it errors out, and says

Can't remove mailbox search  because there is still at least one mailbox on In-Place Hold.

remove-mailboxsearch will give you the same error, well it has to be disabled first!

Here is a fix:

Set-MailboxSearch   -SourceMailboxes  -InPlaceHoldEnabled $false

If the in-place hold name is "test1" and the last mailbox that are in the in-place hold is "testuser"

Set-MailboxSearch "test1" -SourceMailboxes "testuser" -InPlaceHoldEnabled $false

now remove the in-place hold.