It is possible to add a non active item to a workshop job by means of manually entering the sku into the scan box.
Note that non active items will not be added to a purchase order.
A problem has arisen multiple times when items for workshop jobs haven't been coming up on purchase orders leading to a few understandably disgruntled customers when the bringing their bikes in to find the parts aren't here...
It probably is useful to allow inactive items to be added, so long as the guys can highlight that the item needs to be made 'active' in store so it gets ordered by way of a message similar to that in POS.
I don't think this is really a 'would be nice if' request, personally I'd consider it a flaw in the system that needs to be addressed.
Citrus Lime Feedback within Chat for additional context:
I believe that the coding for this pop-up to appear in the Workshop Module in the same way as in the POS Till does not currently exist, and so this would be treated as a new feature request.
I would certainly encourage you to add this to our Feedback Forum, as I can see how this could be handy for all using the platform.
I'd recommend including the POS pop up in the post (detailed in https://howto.citruslime.com/41967-transactions/367031-cloud-pos-adding-an-inactive-item-to-the-point-of-sale?from_search=91036853), and requesting an equivalent be added to the Workshop Module.