You cannot add Sync Filters manually. Those are created automatically based on certain instances that occur while AutoTrading. For example, if you chose to not enter open positions when starting up AutoTrade, a Sync Filter is created to prevent you from joining the existing positions.
That being said, although Sync Filters cannot be manually created, they can be managed by you.
AutoTrade -> Control Panel -> Advanced: Sync Manager button
If you do not see the button, this means you do not have any Sync Filters to manage.
Please keep in mind that if you remove a Sync Filter, you cannot re-create. Please pay extra attention to what you are doing before you actually delete a filter. Deleting filters will result in AutoSync taking action. Anything that the filter was "preventing" will no longer be in place and AutoSync will do its magic and get your account in sync with the strategy now that the filter is deleted.