You can enable and disable different Labs-features by going to your Account Settings, and then navigating to Labs.
These experimental features may change or be removed at any time.

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GitHub Branch Switching

By enabling GitHub Branch Switching you can select the branch that Lovable edits. Once enabled you can switch branch by following these steps.
  1. Go to the Settings of a project
  2. Go to GitHub tab
  3. Click the branch dropdown, and choose the branch you want to switch to
Lovable defaults to synching with the “main” branch