Amazon does allow you to set a restock date on your listings, but SKULabs stock sync will overwrite that date the next time it runs for those listings. There are two possible workarounds for this:
Option 1:
SKULabs syncs restock date and quantity when all of the following conditions are met:
The item must be out of stock
The restock quantity must be greater than 0
The restock date must be in the future.
Set the restock date and quantity for these listings in SKULabs so that SKULabs syncs the restock date and quantity to Amazon.
In SKULabs, navigate to Inventory page > Listings tab
Search or filter to the listing you want to update and click on its name
Find the Listing Rules panel and click on the edit button
Enter the Restock date in UTC time using this format
2020-07-18T13:18:40Zor in your local time zone using this format2020-07-18T13:18:40-05:00.Enter the Restock quantity, then Save.
Option 2:
Open the relevant listings in SKULabs and set their stock sync rules to skip. This will exclude those listings from SKULabs stock sync until you change the rule back. Now you can set your restock date for those listings on Amazon.
Don't forget to return to SKULabs when each restock date is met so you can re-enable inventory sync once you've received the relevant item's stock.