I am trying to set up an email (or Slack!) notification whenever we do a custom/quick sale on the Shopify POS. The reason is that I need to look at those sales that do not have an item attached to them for accounting purposes. It is just too crazy to try to go individually through each order and see if it has custom items. Is this possible?
As no one has jumped in, let me suggest a couple of approaches.
If what you actually need (or could make do with) is a live report which showed your custom sales for a period - say today, yesterday, this week etc - then you could explore the Shopify App Store for an app which supported that kind of custom reporting. There seems to be a few that might do what you want. I picked one at random (called Report Toaster), installed it on our store and was able to produce a report that just showed the Custom Sale line items from our orders. A bit fiddley to set up, but it worked (for our store anyway).
On the other hand, if you definitely need a Slack or Email notification when someone rings up a Custom Sale on the POS, then you could look for an app that might do that (Smart Order Notifications, for example, looks like a possibility, although I didn't try it). Otherwise, you could ask someone to write some custom code for you, which wouldn't be too difficult for an experienced developer.
I would recommend our app Better Reports for this! We can create a custom report filtered to only show custom sale lines by order. You can schedule this to send a daily report automatically to your email or Google sheets showing all custom sales from the previous day.
In addition to custom reporting capabilities, Better Reports offers more than 60 built-in reports that cover your most common reporting needs including sales, current inventory, refunds, payouts, and more. Our reports can even be scheduled to send at a set frequency to your email or Google Drive!
I encourage you to install Better Reports and start your free 14-day trial and I'll be happy to set this up for you.