I am a little confused as to what you are exactly looking for.
Are you talking about saving a specific sketch that can be used to create
a part? I ask because the term "block" has been thrown around lately
ans has meant everything from blocks of text to symbol type blocks.
So I am just trying to get a clearer understanding as to what kind of block you are speaking to.
If you are talking about the saving the sketch type in "saving sketches in the design table"
in the help file and that will give you the steps needed.
See the attached part. It contains a sketches that were converted into 2 blocks. The one name cam contains a path on the outer parameter where the other block travels along. I need to create parts from these blocks and have the parts animate as they do in this block layout. Try to rotate the block named cam (the center point of the big diameter is fixed) by picking the small diameter end and rotate around the large circle and you'll see what I'm talking about.
Blocks_Path_Cam.SLDPRT.zip 27.9 KB
Motion for Layout Sketches works for block only. If you convert them into part, they will be fixed part (until you change the layout). So for your requirement, model them as separate parts and assemble them for the required motion in an assembly.