If you need to set several SKUs as non-replenishable and have that information in a spreadsheet, you can bulk upload the information to Inventory Planner.
Create a spreadsheet that has one column with the SKU (or other unique identifier) and one column with the replenishment status. For items to be marked as non-replenishable, enter '1' or 'true' in that column. Your spreadsheet must have column names in the first row.
In Replenishment, click on Import in the bottom left corner.
Then Replenishment from Import options.
Attach your spreadsheet and choose the appropriate column name for each field. Replenishment status will be noted in the "Hide in replenishment column (optional)" field.
Finally, click Upload to update information.