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:
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.
Navigate to Inventory page Listings tab
Reset filters, if needed.
Find the listing to link by searching the listings table by listing SKU or name
Click on the listing / variant name to open the listing page
Find the Rules section and click on Edit
Enter Restock date using this format
2020-07-18T13:18:40Zin UTC time or this format
2020-07-18T13:18:40-05:00in your local time zone.
Enter the Restock quantity, then Save.
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.