> Is there any way to search for all attributes _except_ a certain value?

If you mean "search all attrubutes except one specific attribute" then the
answer is no.

> Can "Display" links work with multiple options? 
>
> "ABC | DEF" is currently one link.
>
> Ideally, it would be two links, each formatted per the "Display" string.

I don't understand your qyestion. You have an attribute with MOptions, so you
get "ABC | DEF" displayed in the list view. All links in each line point to
the individual entry, so what is the benefit of having two links for ABC and DEF?

> Is there a way to disable wildcard matching in searches?
> A search for "1" returns "1" and "10" and "11".  
> Is there a way to perform an explict match?
> Could there be a numeric match if the attribute type is numeric?

That should all be possible with the build-in regular expression. Just type

\b1\b

where "\b" means "word boundary". I agree that a numerical comparison for
numerical attributes would be better, I will put that on the to-do list.

> Could there be a multi-value option for free text fields, e.g. comma-
> separated?  This would allow multi-parent relationships between log items. 
> 
> E.g. specifying 12, 15 as a value would create unique Display links 
> for "12" and "15", based on the Display specification for that attribute.
> 
> This would be like "multiple fixed options", for the purpose of formatting.

Again, this is not clear to me. What do you mean by "display specification"?
Is it the "List display = ..." option or the "Format attribute = ..." option?
What is a "multi-parent relationship"? Why do you need multiple options for a
free text field? Why can't you use the MOptions specification?