the way to go is to use Matryx's mod chooser, which does what you describe without you having to change the path.txt each time. simply find a post here by Matryx and his signature has a link to the program.
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...the green, sticky spawn of the stars
(with apologies to H.P.L.)
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The Unofficial Space Empires 4 Mod Utility V2.0
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Download as a .ZIP <HERE>
Download as a .RAR <HERE>
Download as a .ACE <HERE>
Check a Screenshot of it<HERE>
Check an Alpha Shot of my Mod Editor (Unreleased) <HERE>
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The Unofficial Space Empires 4 Mod Utility V2.26
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Download as a .ZIP -(HERE)-