That one's quite good, only a few necessary changes from iancoleman's BIP39 tool. (commits: github.com/FarCanary/ElectrumSeedTester/commits/master)

I wouldn't use it outside of testing purposes though.
And the author somehow decided not to include Electrum seed generation which is different from BIP39, so he purposely disabled the "Generate" button.
That reduces the functionality of the tool for testing.

You can disable that security feature in: "Tools->Preferences->Misc->Prevent Screenshots"