From bug 161049 comment 8: The whole dialog does not remember its (customized) size either.
This seems to have started (last time...) in 24.2 with https://git.libreoffice.org/core/+/f1f2a3faeaddf9e9a59f44bf9de38a1f0aa97104 commit f1f2a3faeaddf9e9a59f44bf9de38a1f0aa97104 [log] author Andreas Heinisch <andreas.heinisch@yahoo.de> Fri Oct 06 20:52:15 2023 +0200 committer Andreas Heinisch <andreas.heinisch@yahoo.de> Sat Oct 07 08:49:32 2023 +0200 Revert "tdf#149598 - Remember window state of the format cell dialog" This reverts commit c1893df42567c260ca5fb069038d1a55616e7b7f. Reason for revert: causes a regression under Linux (Bug 156710) https://bugs.documentfoundation.org/show_bug.cgi?id=156710 So what we see now is bug 149598, not a regression from the vertical tab dialogs work. *** This bug has been marked as a duplicate of bug 149598 ***
FWIW, this report was directly related to the implementation of "Vertical Tabs", and not as a generic report about whatever other changes might impact the possibility of re-sizing (and remembering the size) of the Format Cells dialog. Incidentally, as a user, I still do not see any positive benefit of the Vertical Tabs layout applied to the format Cells dialog (more so when the implementation is not complete), while there are negative effects. Perhaps there is such potential positive impact when the change is seen from the perspective of developers – is there any? – but not as a user.