I made some big changes in the PLC program, and sometime soon I have to sort through the
"For Provider [edge] tags" and remove the obsolete tags. These tags were brought in in mass at the beginning as a way to accomplish an assembly-line type of construction. Some ended up being used, and a bunch have not been used. I'm still getting familiar with Ignition. Is there a easy way to quickly distinguish which tags have not been used on any screens?
Ignition Edge: Vision
Assuming all used tags have good quality and unused tags (being removed from the PLC) have bad quality, I would use the tag report tool.
https://docs.inductiveautomation.com/display/DOC81/Tag+Report+Tool
If unused tags are still in the PLC and/or have good quality, then you can try the tag reference tracker option, available since 8.1.34.
If you have scripts that read or write to tags using dynamically created tag paths, then they probably won't show up using a tool such as the tag reference tracker. If you aren't doing anything like that, you don't have anything to worry about, but it is something to keep in mind.
That's explicitly what the tag reference tracker is for.
The tag report tool won't be able to statically analyze complex references, but the tag reference tracker deliberately works "backwards" - every usage of a tag is "bookmarked" with as much identifying context as we can provide. For Vision clients in particular, that's not much, but you will at least be able to tell whether a given tag is ever used.
I stand corrected. Could be very useful in projects that use a lot of scripting.