To mark your products as not sellable on your Mobile Sales App you will need to set the product up as not sellable on the web app.
In the web app, go into the variant view of the product you wish to edit and uncheck the box "This item is sellable".
Save the product.
On your mobile sales app, the variant will now reflect the change and read "Not sellable".
The “not sellable” variant will also not show up in the Cart ‘quick add variant’ list.
Now, you can also check the sellable status of the variant by clicking on More info. You will see the status of the variant indicating YES or NO under Sellable.