Which platform do you use and which browser (exact version)?
If possible, please write a bugreport on the github page which is more appropriate to discuss technical details.

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Edit: In bookmark-dupes-5.5, there will be a special replacement text $TITLE which can be used to find “dupes” with the same title. The github page contains already more detailed instructions and a test version.

With bookmark-dupes-5.4, if you are looking for dupes with a _particular_ title (and not for duplicate titles in general), you can create a “modify” rule which checks for this title and replaces the whole URL by a fixed string. You need to fill the following fields for this rule:

“Name matches”: “\0NAME$” (without quotes; NAME is the name you are looking for; write \ in front of every non-letter).
“Replace URL matches”: “.+” (without quotes; this matches the whole URL)
“By” “x” (here, x can be any nonempty dummy text; in bookmark-dupes-5.5, x can even be empty (which was currently not supported due to misguided “safety” considerations)).

Instead of “Name matches” you can also use an URL match for the part which all bookmarks you want to "match" have in common. Or you can simply replace in your example the page number by an empty string, leaving the (common) rest of the URL as it is.

The latter is IMHO the solution which should be preferred, because it is is least likely to give wrong positives, but you need a rule especially adapted for your URL.

Duplicates are allowed. What you probably want to achieve is that certain duplicates are not removed or not listed. Both can be done in recent versions:

1. If your duplicates are all within one folder, you can e.g. unmark all bookmarks from that folder: Choose the folder from "-- Select a folder ..." to get the corresponding unmark button.

2. To not list the bookmarks in the first place, you have to use “expert mode”. Switch all default rules to “off” (or delete them), and create a new “filter” rule. Into "Name matches" of that rule you can insert e.g. "\0Frequently used\0" if all your duplicates which you want to ignore are contained in folder(s) named “Frequently used”. You can specify your desired exceptions much more fine-grained (using regular expressions for the full path of the rules). To preserve your setting, you have to store it (locally or remotely).

Actually, the default rules in “Expert mode” already contain an example of a “filter” rule with “typical” names for such folders.

Edit: After re-reading your comment now I realized that I had probably misunderstood it. It seems to me that you request a functionality to remove "dead" bookmarks.

As I had already replied to a previous comment requesting this, I had already played with such checks. But there are so much inherent difficulties (URLs responding in nonstandard ways, temporarily delayed, replying only when certain context strings are sent, etc.) that this would require a lot of fine-grained configuration options to work properly, and it would completely shift the focus of the extension. Also, it would require permissions which IMHO are not appropriate for the extension.

There are other extensions specialized only on such checking. I recommend to use these instead.