First please know that I've searched the forum for an answer before asking my question, and found a couple similar scenarios, but not this same one.
EDITED FOR CLARITY: I apologize for this oversight, but I failed to mention in the body of the question that I'm using the new "Tab and Slot" feature in SW2018, rather than the old "Tab" feature, or perhaps creating all these features manually. The first person who replied with a fix for the scenario below likely did not realize that.
I have multiple instances of a weld gusset, which needs slots for its tabs in several separate parts. As you can see below, the tabs are there (in the second picture), but no slots, and no way to make them from that gusset edge (again).
I had some brief success with making configurations of the gusset, naming them Tab-1, Tab-2, etc., but errors came up when I put it through the paces of trying to modify the 'Tab and Slot' features in the assembly context, selected in 'Edit Part'. However, even if it had been successful, who wants to make multiple configurations of Tabs and Slots? Sometimes there may be just a couple, but conceivably there could be dozens.
Interestingly, this scenario is VERY common in the sheet metal welding industry, and shouldn't need a "workaround" or a "fix", as it should be part of the original feature intent. Maybe it is, and I simply haven't found it, so if you know, please pass on the procedure.