So sorry to hear this Eileen. Although you are finding it frustrating, it is not stopping you having healthy vegetables. But I wonder, is your cold frame in full light or ithere a tall wall or tree nearby? Any light reduction tends to draw plants upwards or to one side, with longer stems.
All this is one reason I recommend pricking out because when doing that, you can bury any long stems and create a sturdy seedling. Then again, when you plant you can make a deeper hole and bury the stem again.
Your plants may be ok in the cold frame without being brought out every day, and at this time of year you don’t need to worry about night temperatures: I haven’t shut my greenhouse or polytunnel by night for well over a month.
One other possible cause of legginess can be nutrient poor compost which makes plants generally thinner. Do your young plants make healthy green leaves before being plantied?