In Arborist, tools are configured globally to work across any worktree of any repository. The idea is that you likely have a common set of apps that you use regardless of the project you’re working on. For example, an iOS developer may have Xcode, a git application, a terminal, and a secondary IDE such as Nova or VS Code open all at once.
Tools provide quick actions to open the currently-selected worktree with a specific tool so that you have easy access to spin up all the apps you need to work on your worktree. Tools are configured in the Settings of Arborist:
Notice in the bottom section called “Launch” that you can customize the arguments passed to the tool when it is activated, and there is an option to “Close windows before launch”. This option tells Arborist to attempt to close all the currently open windows that app has before opening the selected worktree. This is a handy way of ensuring that the tool only has your selected worktree opened, with the goal of reducing confusion between worktrees that belong to the same repository but are different checkouts.