If you don’t want a record in your stash anymore then you can delete it. Depending on your reason, it may be a better idea to update the status (e.g. for a Fabric you can change the status from “Uncut” to “Used”), this way you will still have a record of it, but it won’t be shown by default.
To delete a record, navigate to the record in question, click the three dots in the top right and select “Delete”. You will be shown a confirmation dialog because the action is irreversible. If you’re sure then click “Delete” to confirm.