How to Enable Substring Matching in PowerShell Tab Completion?

I'm trying to modify PowerShell's tab completion behavior so that it doesn't just match from the beginning of a word but also allows substring matching

Example

• Normally, if I type under<TAB>, PowerShell won't suggest code-understanding because it doesn't start with under
• I would like PowerShell to suggest any word that contains my input anywhere (e.g., code-understanding, file-underlined, etc.)

What I've Tried

I've already set up PSReadLine enhancements for better menu-style completion :

Set-PSReadLineKeyHandler -Key Tab -Function MenuComplete

This improves predictions but still only matches the start of words

My Question

Is there a native way in PowerShell 7+ to make TAB completion match substrings instead of just the start of a word ?

tl;dr

Mathias has provided the crucial pointer:

PowerShell's tab completion (aka command completion) supports wildcard expressions so that - rather than trying to roll a complication custom solution - you can simply prefix your substring with *; to use your example:

*underTab will complete to both code-understanding and file-underlined (repeatedly pressing Tab cycles through the matches; with your custom Set-PSReadLineKeyHandler -Key Tab -Function MenuComplete, all completions will be presented in a menu).

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Background information:

Wildcard-based command completion:

• With literal strings, PowerShell's command completion uses prefix matching, i.e. the input string must match the start of commands.

  • Expressed in wildcard terms, underTab behaves like (Get-Command).Name -like 'under*', i.e. a trailing * is implied.

• Wildcard expressions are matched as such (except that a trailing * is always implied), and a preceding * therefore effectively performs substring matching, i.e. the literal part is matched anywhere in command names.

  • You can even use wildcard metacharacters multiple times; e.g., *readl*handlerTab completes to Get-PSReadLineKeyHandler, Remove-PSReadLineKeyHandler, and Set-PSReadLineKeyHandler.

Capitals-based command completion:

PowerShell (Core) 7 offers a little-known command-completion method based on matching capital letters in command names.

E.g., t-mm completes Test-ModuleManifest, but note the following:

• The capital of the verb part of the command name (Test in this example) must be followed by -

• Every capital letter must be specified (in order) in order to match a command name; e.g., s-t completes to Start-Transcript and Stop-Transcript, but not to Start-ThreadJob, because the latter has one additional capital, J (that is, s-tj is needed to match it).

• This approach can not be combined with wildcards.

Also note that many built-in cmdlets come with superficially similar aliases that use a standardized alias prefix that is defined for each approved verb, e.g. sa for Start-, followed by - without an intervening - - a non-standardized (sequence of) letter(s) for the noun part. E.g., jb is used to represent the Job part in Start-Job.
That is, submitting alias sajb as-is is an alternative to using capital-based command completion with
s-jTab.
To see which alias(es), if any, are defined for a given command, use
Get-Alias -Definition <command-name>

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^{[1] Note that the completion works even with non-approved verbs.}