Before saving the final version, run the Joukey GM Checksum Plugin. It will scan the modified areas and update the checksum block at the end of the file.
Once the plugin is active, using it is straightforward. joukey gm checksum plugin
Helping players modify resources in games that have basic integrity checks. Script Integration: Before saving the final version, run the Joukey
The plugin's author, joukoy , has noted that "most 'LS' XDF files are using plugin created by Antus / PCMHacking.net, not my P01/P59". Before saving the final version
If your XDF isn't working with the joukey plugin, it may simply be that the XDF was created for a different, albeit functionally similar, plugin. This situation has resulted in four or five different GM checksum plugins with different GUIDs being distributed across the internet.