We currently have a software-version tag (with 21 questions) which has no tag wiki or even an excerpt to guide us in its usage.
Do we need it and, if so, when should it be used?
It looks like the usage within the few questions it does have are about differences between different versions of a software/application or where to find specific versions of software.
In the first case, the software/application tag is probably sufficient and some of those tags have version specific tags as well that should be used
For example, "How do I do A from version X in newer version Y?" should be tagged with version Y (if it exists) or just the appropriate application tag.
The second case would be similar, if it's on-topic.