According to the FAQ for the PSTK, the offiical support channel and feature enhancement request method is the community site. However, as a workaround, you could use Invoke-NcSystemApi to set a count higher than the limit imposed by the Add-NcSnapshotPolicySchedule cmdlet. For example, on an ONTAP 9.6 system:
PS H:\> Get-NcSnapshotPolicy
Policy Enabled SnapshotPolicySchedules
------ ------- -----------------------
custom True {hourly (1)}
$PolicyName = "custom"
$Count = "300"
$Schedule = "daily"
$Request = @"
<snapshot-policy-add-schedule>
<count>$Count</count>
<policy>$PolicyName</policy>
<schedule>$Schedule</schedule>
</snapshot-policy-add-schedule>
"@
Invoke-NcSystemApi -Request $Request
PS H:\> Get-NcSnapshotPolicy
Policy Enabled SnapshotPolicySchedules
------ ------- -----------------------
custom True {hourly (1), daily (300)}