I am having some slight issue using the query
adb shell content query --uri content://browser/bookmarks" & "adb shell content query --uri content://browser/searches I have played around with the browser and added some bookmarks, but I am receiving nothing in return. Does anyone have encounter any issue using the queries?
according to the chromium issuetracker, that API got deprecated.
The alternative in userdebug / eng builds is using adb root to get the full sqlite History file from the apps data directory and query that instead. But that is for developers and some customrom users only.
adb pull /data/data/com.android.chrome/app_chrome/Default/History 
com.android.chrome is specific to Chrome, not browser mentioned in the question. Though, now I can see that the browser URI mentioned in the question might be unclear, if it's literally browser, or just a generic placeholder for the browser's package.
browsercontent provider is not always utilized by all browsers, maybe AOSP Browser though. What browser are you using?