Where in "Define modeling conventions" can we turn off the check for end events for sub-processes.
Technically there is no rule, which you could configure, to check specifically sub-processes. The only thing I could imagine is modelling rule 4.8 which checks if there is a start and end event within a process. But this would only warn you when you are working and saving the sub-process itself. In this case, this is a normal behavior because technically the tool does not know if the process you are working on is a sub-process.
KBA , BPI-SIG-PM-MOD-EDT , Graphical Editor for SAP Signavio Process Manager , How To