From SimBrief User Guide:
Route Formats
Generally, SimBrief routes should be entered with all waypoints and airways separated by a single space. For example, BANGR9 PANGL YZT J502 PRYCE BKA 59N140W JOH WITTI4.
In the route above, BANGR9 is the SID, PANGL is the first waypoint, J502 is the airway connecting YZT and PRYCE, and WITTI4 is the STAR. There is no airway between PANGL and YZT, which means we would simply fly direct between these 2 waypoints. It is also fine to write this route segment as PANGL DCT YZT. DCT is the standard ICAO identifier for Direct, but SimBrief normally omits the DCT in its route suggestions for simplicity.
59N140W is a custom lat/long waypoint which translates to 59° North by 140° West. More precise coordinates can also be entered, for example: 59°17’30"N 140°32’12"W can be entered as 591730N1403212W.
Place/Bearing/Distance waypoints can be entered using the following format: JFK270020. In this case, a custom waypoint would be positioned on the 270 degree radial at 20 nautical miles from the JFK VOR.
For oceanic flights, North Atlantic Tracks (NATs) can be entered as airways in the route string. For example, NATU stands for Track Uniform in the following route: GREKI JUDDS MARTN TOPPS N557A NEEKO NATU GISTI SLANY UL9 STU P2 BEDEK BEDE1H.
See also Converter for Google Maps Coordinates
Cheers
Ian