After running a few autocross laps with the parking brake partially engaged, I made a note to install a parking brake switch. My version was to install a small limit switch on the parking brake housing and an ABS plunger on the E brake handle.
I cut a block of ABS as shown and glued to the E-brake handle using JB Weld, a limit switch with a lever is glued to the E-brake housing as shown. Make sure the locations are close enough that bending the switch lever will adjust the system so the light goes out as the handle is fully seated.
I used the existing brake fail lamp as the indicator. It turns on when the Red/Black wire, on the lamp is grounded. Connect the common terminal, on the limit switch, to any ground. Connect the normally closed terminal to the Red/Black wire on the brake fail lamp. When the parking lever is puller out, the light will turn on.
Parts I used.
SPDT Limit Switch similar to
https://www.digikey.com/en/products/detail/traktronix/0306-00120/16546497.25” ABS scrap
JB Weld (glue the AMS to the E brake handle.
Ron