This is a known issue with many threads about it. See:
Hey I have a question. I've seen people, like the Youtuber Jayborino, play a myriad of campaigns meant for different versions of Warcraft 3. Both reforged and earlier editions. I've tried getting both to run on my own device but the Reforged always updates my 1.31 file. Is there a way to have...
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If you have run reforged once since last time you were in editor, you need to delete a register key (open regedit, find: Computer\HKEY_CURRENT_USER\SOFTWARE\Blizzard Entertainment\WorldEdit, and delete: "Tool Windows").