If the Purple Cube (Run Minecraft) button is not visible in the VS Studio Code, then try the following steps to fix the issue:
1. Go to the below link and download the CodaKidForge extension.
2. Open VS Studio Code > Click View > Extensions > click the three little dots in the upper right of the EXTENSIONS pane > Click Install from VSIX > Select the newly downloaded codakidforge-0.0.4.vsix file.