I do not know for sure but afaik the jumper pins are designed to be binary and not one way switch only.  I imagine if the board could be bricked by simply moving jumper there would be clear warning alert user not to do it.  there is none. Inspiron 3650 has such MECLR1 jumper that user found out can be used to revive a bricked board that had a failed bios update.  details still lacking and it is considered a programmer’s back door. please note this is a undocumented area for professional (hacker) only and not for ordinary user, so take your risk.  perhaps you can share the reason why you want to enter service mode.
How do I put a Dell 3010 SFF into Service Mode?
How to put Dell 3010 SFF into Service Mode