How to delete products inside a channel?
If you delete/move some listings (with the sync function off) from any channel: Nembol has no way to know it. So Nembol thinks those listings are still there.
This causes nothing besides the fact that at the first edit of any of those listings, Nembol will receive an error back from this channel saying “Hey, this listing is not here anymore” and the listing will STOP syncing. The latter is important for you IF and only if any of those listings are also on other channels.
Solution:
Consider delisting listings using Nembol.
Select those listings in Nembol
Pick “delist” from the Actions menu
This will delete the listing from the chosen channel, but keep it on other channels.