I tend to obsessively design my own ships, even the colony ships and constructors.  I will often have multiple designs for both colony ships and constructors, in fact -- generally a more expensive longer-range version of each to colonize/build starbases in farther removed from my current colonies (so they will have more life support modules) and cheaper versions to colonize star systems/build starbases closer to my current colonies.  I tweak how they are outfitted as my engines, life support systems and miniaturization allow.

I honestly never build the pre-designed ships, and those honestly become annoying spam in my ship list to build particularly as I get enough techs that I have to scroll through a lot of them, as well as when I'm looking for my designed ships to update them.

Similarly, two games rarely play out the same, and every time I start a new game, I wind up deleting my saved designs that load into my list of buildable ships whenever I reach some tech to make them buildable.  I don't trust that one or more of the components on the ship aren't already exceeded by the technologies I have researched (as there are so many techs, as well as some precursor artifacts or other events that can affect tech), or I may have different priorities in terms of range/speed/capacity/etc. than I had in the previous game.  The designs I make that persist game to game also become annoying spam to me.

I would request/suggest that auto-designed ships and loading custom designed ships from previous games be toggleabe, so that those of us who wish to have a clean list of ships to build, and only have a list of ships I have designed for the current game.

Thanks for considering my suggestion!