Some data points:
The latest version of the standard (issue 8) has "The -a and -o binary primaries and the '(' and ')' operators have been removed." instead of "obsoleted" https://pubs.opengroup.org/onlinepubs/9799919799/utilities/test.html

test -a is not a POSIX construct, I intentionally avoided it.

Thanks for fixing this.

@ametzler1 Thank you for your report.
I modified a bit (not using && between two test but using -a for a single test command), and pushed the change:
rP121494245f49: build: Allow build with fltk 1.4.

In the meantime pinentry has been updated also for VSD 3.4.

Looks good to me on GnuPG-VS-Desktop-3.3.90.8-Beta-Standard.msi (3.3.3 betaversion) @ win10

nr.1
nr.2
schwarz
weiß

works in vsd3.3.3, tested with VS-Desktop-3.3.90.8-Beta

The gold rule of tab order is that tab order follows the usual reading direction, i.e. line by line from left to right. If you press Enter after entering the password in the first input field then the focus should jump to the second input field.

Looks good to me on gpg4win-5.0.0-beta357 @ win10:

The fix should be available in gpg4win-5.0.0-beta350.

Noteworthy changes in version 1.3.2 (2025-07-28)

not sure if this really is an issue, maybe for a person proficient with a a screenreader the behavior ist ok, after the fix of the show/hide button is done?

This has been fixed in pinentry-qt5 (which is used by VSD 3.x).