A suggestion to have a debug connector on future Dongle development hardware.

[Supermath101]

On future revisions of the nRF52840 Dongle, and on future development hardware of a similar form factor, I'd recommend putting a debug connector that's compatible with the Raspberry Pi 3-pin Debug Connector Specification (https://datasheets.raspberrypi.com/debug/debug-connector-specification.pdf), instead of the existing pair of castellated edge holes.

[Turbo J]

Bad idea to only use 3 wires, especially on a product that runs 1.8V after a complete memory erase. 

You need at least 5 pins: 2 for SWD, Reset, VCC and GND. Reset is required to "unlock" the chip in some situations. VCC adapts the debugger input voltage to the levels on the dongle. 

The hardware has one of the "standard" ARM footprints for a 10-pin header on the backside. Most compatible debugger products support this plug out-of-the-box.

[Supermath101]

I never specified that the 10-pin footprint should be removed. If you need to programmatically reset the nRF52840, just use that. As for the 1.8V voltage, the specification I linked earlier says this:

"Hosts and targets using these interfaces MUST have 3.3V failsafe pads. (Failsafe means that even if
the host or debug target is unpowered, the pins will survive 3.3V+10% being applied to them
continuously and will not draw any current).
We allow a debug target to work at lower voltages, say 2.5V or 1.8V, but in this case, as before, the
pins used MUST still be both 3.3V tolerant and failsafe to 3.3V (plus 10%). …"

Now, I don't know whether the nRF52840 (or other chips used on future Dongle development hardware) meets those specifications or not. If they don't, then this recommendation can be ignored.