There are a handful of things that I think TC has gotten 100% correct, as far as implementation and configuration is concerned.
GUI QuickFilter is probably vague, and even in that case TC isn't optimum as it's own implementation refuses to permit Regex - even though it has a regex library and you can use it almost everywhere else. Anyways, Idigress somewhat...
GUI QuickFilter (with Regex), a simple ":" as the leading character within MC's [*.*] Filter in the panel status bar, to indicate using Regex instead of "glob" or Windows CMD like ? (single char) * (any char).
As is the Filter implementation already has a number of fancier-than-most filtering type capabilities. What would perfect it (nearly) would be the "funnel" icon when clicked, toggles between:
1) Hide All Files that don't match 'this string' (where the string *could* be a regex). OR
2) Jump to the file that matches 'this string' --- instead of hiding files.
3) A single Toggle checkbox to the left of the [*.*] filter, that enables the filter to be
---> a) Normal: Only show files that match.
---> b) Exclusion: Only show files that DO NOT match (the [*.*] filter).
The "toggle state" of the Funnel Icon would be static.
The ability to filter OUT and filter IN is something that few tools enable --- yet its a very powerful concept, similiar (to me, in power at least) in how
1) EmEditor allows one to do multiple regex's in batch (one after the other), along with an interface to save those regex batches for future use.
2) Most old usenet readers scoring capabilities.
3) Opera M2 mail's filtering
4) Any tool that allows multiple 'FIND' criteria, where the match can be indicated as:
----> EqualTo, >=,<=, <, >, NotEqualTo.
[OT]:
I frequently find myself annoyed at online shopping for instance, as almost no Store (none that I have seen at least) allow one to filter OUT, only the ability to filter IN (exclude things that don't have X-trait).