I need to use the SoftwareSerial library to interface with an rs232 device because the software serial device can invert the signal for me before its read.
Is there a way to make the SoftwareSerial or NewSoftwareSerial library compatible with the hologram dash?
Its unlikely this will happen as the Dash is depreciated and no longer supported. I believe all the dash hardware and software is open source so your best bet is to do it yourself or switch to a different, supported product.
The Arduino MKR 1400 and MKR 1500 seem to be very similar to the Dash and are actively supported (by Arduino).