Improved output for 'Format string' field in Convert > "Tag - Filename" dialog

In the Convert > "Tag - Filename" Dialog, I'm finding the "Format string:" dropdown field extremely frustrating to use, especially since I'm using advanced formatting in several of my expressions, that look similar code-wise, but formats the outputs differently.

I feel drastic improvements need to be made to this dialog, so you can instantly tell what the expression you're selecting does, without waiting to preview the output via Tooltip popup, or having to mentally keep track of which expression does what by the order it appears in the dropdown.

Even as a short-term fix, making the dropdown display the output string by default, rather than the code syntax, would make this dialog infinitely more usable.

Ideally though, the dropdown should be split into 3 separate data fields, so you can:

  1. define a custom name for each expression,
  2. preview how the expression will output
  3. a block for code syntax (ie. not just a text field/dropdown)

In the long-term, what would be great is to see a separate Expressions manager that allows you to define custom snippets to re-use in this/these tag/filename dialogs, that could allow you to better organise these expressions, import/export, etc.

If you have certain expressions that you use again and again, it may be worthwhile to consider to use an action instead of the converter.
An action of the type "Format value" for _FILENAME leads to the same result as Convert>Tag-Filename.
As you can define a user-defined name, you have the custom name.
I think that the preview is then not necessary any more as you tested the expression already in the converter and summarized the purpose in the user-defined name.