Index -> Interface -> Filters & Search Options -> Tech Sliders
The top of the Filters & Search panel has five symbols next to colored bars, listing the five techs in the game. The techs are, from top to bottom, Order, Mind, Life, Cyber, and Entropy.
By clicking on the red button next to a tech symbol, you can filter out all of those cards. (For example: Clicking on the button next to Entropy, will hide all cards that have Entropy in their cost.)
By moving the sliders, you can filter out cards by their tech cost. Moving the left-most slider to the right filters out cards that don't meet a minimum cost, while moving the right-most slider to the left filters out cards that exceed a certain cost. (For example: Moving the left-most slider of the Mind bar two notches and the right-most slider three notches will make it so the only cards you see with Mind in their cost will cost at least 2 Mind, but no more than 6 Mind.)
Tech Sliders default to showing all cards of all tech costs. If you're in the Deck Builder and you set a race for your deck, the Tech Sliders will be set automatically to show only the cards of that race and its two techs.
Reset Button
This button resets the Tech Sliders, plus all filters and search criteria. All cards will again be displayed.