Another point for the wish list: I am looking for an integrated password analysis tool that evaluates the passwords in my database both for their equality or similarity among themselves, their password strength as well as their age.

Regarding the implementation, I can imagine several variants. It could be a separate menu point, over which a test procedure can be started. At the end of the check, the result per database entry is displayed in a list. The list should be filterable according to problem type and criticality.
Another possibility would be to always check the passwords in the background. For each entry, a kind of traffic light (eg green, yellow, red) and, if necessary, a warning message is displayed which indicates how secure the password of an entry is.

Examples of warning messages:

• The password is used several times in the same or similar form (the entries x, y, z... use a related password)
• The password is not strong.
• The password is quite old (the older a password, the higher the probability that it could be stolen in an attack on the vendor).

Edit: The following plugins for the original Keepass try to achieve the same or similiar goals.

• Password Counter
• StrengthReport
• QualityColumn
• QualityHighlighter