PlatformIO Core 3.5.0 introduces many new features and performance improvements. The notable changes are as follows:

• PlatformIO Home - interact with PlatformIO ecosystem using modern and cross-platform GUI:
  • Library Manager:
    • Search for new libraries in PlatformIO Registry
    • "1-click" library installation, per-project libraries, extra storages
    • List installed libraries in multiple storages
    • List built-in libraries (by frameworks)
    • Updates for installed libraries
    • Multiple examples, trending libraries, and more.
  • PlatformIO Projects
  • PIO Account
  • Development platforms, frameworks and board explorer
  • Device Manager: serial, logical, and multicast DNS services
• Integration with Jenkins CI
• New include folder for project's header files (issue #1107)
• Depend on development platform using VSC URL (Git, Mercurial and Subversion) instead of a name in Project Configuration File "platformio.ini". Drop support for *_stage dev/platform names (use VCS URL instead).
• Reinstall/redownload package with a new -f, --force option for platformio lib install and platformio platform install commands (issue #778)
• Handle missed dependencies and provide a solution based on PlatformIO Library Registry (issue #781)
• New setting projects_dir that allows to override a default PIO Home Projects location (issue #1161)
• Library Dependency Finder (LDF):
  • Search for dependencies used in PIO Unit Testing (issue #953)
  • Parse library source file in pair with a header when they have the same name (issue #1175)
  • Handle library dependencies defined as VCS or SemVer in Project Configuration File "platformio.ini"(issue #1155)
  • Added option to configure library Compatible Mode using library.json
• New options for platformio device list command:
  • --serial list available serial ports (default)
  • --logical list logical devices
  • --mdns discover multicast DNS services (issue #463)
• Other bug fixes and performance improvements.

See PlatformIO 3.5 Release Notes for details.