Corner setting is not working for me. Blueprints position always calculated from the middle.

This setting should not work for blueprint.

"To change the center of the blueprint, enable grid size (1x1 is recommended), and set an absolute reference point."

Well, its just strange that deconstruction works for corner but blueprint does not. Requires more unnecessary calculation. Also for items that are not aligned to world grid (from other mods), it gets even more weird when your length of blueprint is even number, in that case they end up between two cells of grid. Calculating from corner would fix that two. Can you please add this option?

I can't do this because of API limitations (there is no easy way to get the blueprint's size in width and height).

There is nothing strange about the differences, since the tools used are different. The deconstruction plan requires you to specify a rectangle, which can be specified in two ways (so there is an appropriate option). The blueprint, on the other hand, requires you to specify only the position where it needs to be placed. Manually (with the mouse), you use these tools in the same way.