How to iterate items of the window with dynamic title
The simplest way is using the Application's bundle identifier. This can be found from reading the Info.plist file within the application package, or with some simple AppleScript such as:

get id of application "TextEdit"


This returns com.apple.TextEdit.

Then, one could run the following AppleScript:

tell application id "com.apple.TextEdit"
    activate
end tell


So, your revised could would look like this (note use of process id since you're using System Events).

-- set bundleId to id of application "AppName"
set bundleId to "com.apple.TextEdit"

tell application id bundleId to activate
tell application "System Events"
    repeat with theProcessId in (processes whose bundle identifier is bundleId)
        tell process id (id of theProcessId)
            tell tab group 1 of window 1
                set items to every row of table 1 of scroll area 1
                set itemValues to {}
                repeat with aRow in items
                    set itemValue to (value of text field 1 of aRow)
                    log itemValue
                    set the end of itemValues to itemValue
                end repeat
            end tell
        end tell
    end repeat
end tell