When I open and read m4l originally attached patches, I found some externals have no help/reference.
Loop Shifter’s [ls.central] seems to useful data storage(?)
Step Sequencer’s [step.overplay] seems plaing some important role too.
I want to know whether I can get some docs of these externals.
Is that unavailable?
No. As you have noticed, there are some undocumented externals and these are going to stay that way.