Simpl doesn't support multi-line, so you have to flatten the message down to one line. However HTTP messages MUST be multi-line to be valid syntax. So in Simpl you add a \n for each line. Like so:
POST /axis-cgi/apidiscovery.cgi HTTP/1.1\nContent-Type: application/json\nUser-Agent: PostmanRuntime/7.34.0\nAccept: */*\nPostman-Token: c2d76ff9-854d-4daf-81d9-5ed4a8035c99\nHost: 10.95.16.11\nAccept-Encoding: gzip, deflate, br\nConnection: keep-alive\nContent-Length: 36\n\n{"method": "getSupportedVersions"}\n\n
