They called, Airconditioning will not be installed today because it’s raining.
But since I was home anyway, I have tried a ton of different syntax for the interpolation.
What finally seems to work for me is
[env]
build_flags=
-D_IR_ENABLE_DEFAULT_=false
-DSEND_NEC=true
; "-DSEND_CHIMEI=true"
; "-DDECODE_NEC=true"
with PURPLE
[env:PURPLE]
platform = espressif32
board = esp32-s3-t-qt-4R2 ; is a Json file with board specifications?
framework = arduino
lib_deps = bblanchon/ArduinoJson@^6.1.0
lib_ldf_mode = chain+
build_flags=
${env.build_flags}
-I include
-D BOARD_HAS_PSRAM
-mfix-esp32-psram-cache-issue
-D ARDUINO_USB_MODE=1
;-D ARDUINO_USB_CDC_ON_BOOT=1
-D ARDUINO_RUNNING_CORE=1
-D ARDUINO_EVENT_RUNNING_CORE=1
-D PurpleBox=1
Gives:
So for some reason it only works if i don’t use single or double quotation marks
edit: your name came up on several questions about the topic 
Thanks for your support