You're free to share those tools here instead of just doing the trite "oh you guys just heard about this"
There's not much to really share. When people build EDH decks they usually focus upon individual cards with effects that interest them (usually commanders) and branch out from there with interactions and synergies as they build out the rest of that deck. The difference between there and cube design is mostly just how deep they're willing to go for specific synergies or unique effects because they're not building with a draft component in mind. What's worth taking away from this isn't the end result, but the card evaluation process where you're looking to maximize the interactions with a given card.
For example, I have a
Karametra, God of Harvests deck that I've had for the last decade. Early on I decided to build an Enchantress subtheme to generate card advantage so I put in cards like
Argothian Enchantress and
Verduran Enchantress because I could curve right to Karametra and draw that extra card to keep gas flowing. To get there even faster I started playing more mana dorks at 1 mana and stuff like
Utopia Sprawl and
Wild Growth. Printings of cards like
Eidolon of Blossoms and
Sythis, Harvest's Hand became doubly exciting because that just padded out the curve even further let me chain off with explosive draws if I sequenced right. Every enchantment body has additional value so card like
Weaver of Harmony or
Shigeki, Jukai Visionary become even more appealing with their additional synergies.
Then I look at other features of Karametra herself that work to my advantage. Anytime I cast a creature I
Rampant Growth out a land with a Forest or Plains typing. Well, if I lean towards fetchable duals this makes something like
Emeria, the Sky Ruin triggers more attainable. If I play a bunch of cheap creatures, I can chain multiple triggers to ramp out way ahead. Or I can do something like sandbag cheap mana dorks in the later game so that I can more quickly rebuild than my opponents if I fire off an
Armageddon or
Ravages of War. If I play
Field of the Dead then I can include a handful of snow-covered basics to ensure that I hit that 7 unique names condition and start generating zombies for free. Buy back fetches with
Ramunap Excavator or
Titania, Protector of Argoth and rebuilding after a wrath could be very quick. It's all the little interactions making the most of what you can get out of individual cards.
This approach can easily be applied to cube as in the examples shown above with
Trade Routes, but only if people get off their weird hatred for EDH as a concept. There have always been good ideas there to take advantage of. You can scour through pages and pages of various commanders on EDHREC to just find deep cuts with interactions and expand from there. It's just another tool to utilize when designing a cube, all comes down to how deep into the weeds you want to go.