r_teroor says:
Yeh welcome in the Mesh editor.
What I do when it happen to me; I take another block that will in the future connect to him, i import it IN the block i'm editing, Then i move a bit the block to a side to let a bit of space between the two ones. Then i take the measures between two points of the blocks. And enter this particular mesure into the "tool step". With the "perfect" lengh then the block will move in the good position... If its not understandable then add me to discord i will show you streaming it