There is a technique in music theory called suspension. Basically your extending the length of one note of a chord, and blending it to the next chord.
Chords are not the only application of course, but I hope you get the idea.
Similar sentiments of this thread were shared at the Pattern Matrix Rethink thread: post #25
If I’ve understood BotB’s description properly,
the issue occurs when he wants to shift a pattern so that it overlaps from one block
unto the next block, so this pattern is in two blocks.
I guess one way to avoid this knot sort of speak,
is to max out your pattern legnth in the hopes that it is enough, and in most cases it will be enough,
to write your musical phrase with this type of compositional technique or edit (suspension, overlap, etc.) in mind.
Just loop the pattern your in with the break pattern command ZB00.
There is the Rotate Pattern tool, perhaps a Shift Pattern would help ?