I would like to ask if this continues to be the case? My company is planning on using the QN9020 BLE microcontroller and I would like to know if it supports multi-drop?
Multi-drop SWD is not supported in standard Cortex-M0, M3 and M4 parts. According to this ARM article:
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.faqs/ka16814.html
The chip vendor (i.e NXP) needs to license (and therefore implement in silicon) an additional component. AFAIK, NXP has not...