MySQL Workbench is originally designed to be a single instance app only. On Windows this has been extended to allow multiple instances (there’s a setting in the preferences) and you found a way to do this on macOS. However this bears some risks, because all instances share the same config and cache files and can write simultaneously to them, which is prone to file corruption. Also, any changes done to the configuration or connections end up in the same file, so the last change may override previously made changes in another instance.
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