Going through this documentation here there is the following statement:
This tool is no longer supported. Instead use Android Studio to create
AVDs and create projects, or use sdkmanager to view and install SDK
packages from the command line.
You can control your Emulator and it's appearance or behavior using below syntax through the command-line.
Here's your emulator
emulator -avd <avd_name> [-<option> [<value>]] ... [-<qemu args>] emulator -list-avds
Launch the emulator:
emulator -avd yourEmulatorName
For ex :
emulator -avd Nexus_6_API_25
See this link to control the
Emulator from the command-line.