There is a problem on SU with Excel questions because clearly some of the community considers most of Excel that is not VBA as off topic (not code) whereas the nearest available to an ‘official’ rule is that worksheet functions for instance, when used in a worksheet, qualify as code.
So for example, the same person who upvotes an answer that provides VBA for a button to click to perform some actions may downvote an answer that explains where to find on the Ribbon a button with the same functionality. (Though obviously I cannot prove this assertion.)
This is presumably contributing to the Close Votes backlog.
Because the boundary is not clear (it is a ‘grey area’) and seems inherently so there is (a) overlap between SO and SU – if avoidable, presumably not desired – and (b) ill-feeling where the different outlooks clash.
I have noted many questions tagged [excel-vba] on SO where the accepted answer did not require VBA. That is, many OPs expect VBA to be required where it is not. There are numerous questions on SO (within some flavour of [excel-vba]) where a workable answer does not require VBA or a worksheet formula, just appreciation of some (admittedly probably little used!) standard feature.
SO>SU was, I believe, the one with far and away the most traffic, when question migration was common.
My sense is that the majority of the more recent questions in the [excel] family being asked on SO have already been answered on either SO or SU, albeit with variations ranging from trivial (eg string manipulation for different length strings) to substantial - for the latter where ‘duplicate’ would IMO be inappropriate.
It has been acknowledged that duplicate posts are a problem. Locating candidates is in general not easy (eg with Titles such as “Formula error”), confirming duplication is time consuming (both questions need to be read and understood and also each difference assessed for significance in itself and in context) and deleting/merging/leaving alone is presumably tedious.
nearly 1000 office related questions on Super User is not an argument that convinces me. Taking tags on SU that contain
excel and double-counting, the total is presently nearly 8,000. On SU about ten times that number. So between the two sites probably several times as many questions as the total for all tags on say Electrical Engineering. And then perhaps the same again or more for the likes of Access/Outlook/PowerPoint/Word etc.
Such volume would seem to count in favour a site for “Office Suite” rather than against it.
Fragmentation of SE, and in particular SO because of Careers, may have economic disadvantages in reducing the market size on SO but the segmentation may offset this with quality enhancement.
“Office Suite” might be a solution to various of the above issues. The likes of a set of tags [excel] [vba] [excel-vba] [macros] [vlookup] might be rendered down to just one, leaving scope for more specific tagging and hence more effective searching.
A new site would also be an opportunity to adapt the ‘rules of the game’. Possibly have more emphasis on wiki Q&As, even possibly be exclusively for canonical questions and answers. Then no change whatsoever to SO and SU, other than allowing link-only answers there, provided the link is to “Office Suite”, and perhaps refusing to accept any Q with a tag that matches one on “Office Suite” that the OP has not visited.
Something like the latter is not presently applied to new users before they are allowed to post, so presumably has drawbacks.
Without the rep motivation a ‘wiki-only’ site would attract hardly any traffic (tag wikis may be a guide) but perhaps that would be acceptable if providing a better experience for SO and SU. Within Excel there are only about a dozen regular contributors – who I image get heartily sick of answering what are basically the same questions over and over again (but nevertheless continue to do so – it is not exactly the OPs fault s/he was not the first to ask!, and after all, rep is rep.) I have already seen where an exceedingly high rep member has posted a very basic Q specifically to post a canonical A as well.
In any case, rep might still be earned just in a different way. Possibly related to the votes cast in favour of A's linking to the post.
Quite what to aim for is not clear to me but one way or another I think there are possibilities worth more than just one comment:
I'd say no there shouldn't be a SE-site specifically for them.