Can beds in the same block have different lengths?

Not in one block, but two blocks do it, and every bed keeps its true length in your plan. All the beds of a field block or greenhouse share one length, one width and one path width.

If part of a garden has shorter beds, along a hedge or a slope, create that part as a second block and name them so your team recognises them, such as B3 and B3 short. Each block has its own beds on the Crop Map, planted the same way.

See Create a field block.