When you build a tree of tasks for the first time during a PyCharm session, the npm tool window is not opened yet.
If you already opened the npm tool window, you can access it with Search everywhere. Press Shift twice to open the search window, start typing your query, for example, npm scripts, and select Show npm scripts from the list.
Alternatively, select View | Tool Windows | npm from the main menu.
The npm tool window opens when you select a package.json file in the Project tool window or open it in the editor and select Show npm Scripts from the context menu.
As soon as you invoke npm, pnpm, or Yarn, the tool starts building a tree of scripts defined within the scripts property of the package.json file on which it was invoked.
If you have several package.json files in your project, you can build a separate script tree for each of them and run scripts without dropping the previously built trees. Each tree is shown under a separate node.
The tool window shows the script output, reports the errors occurred, lists the packages or plugins that have not been found, etc. The name of the last executed script is displayed on the title bar of the tool window.
To build a tree of scripts, do one of the following:
Select the required package.json file in the Project tool window or open it in the editor and choose Show npm Scripts from the context menu.
In the npm tool window, click on the toolbar and choose the required package.json file from the list. By default, PyCharm shows the package.json file in the root of your project. If you have another package.json file, click Choose package.json and select the package.json file you need in the dialog that opens. PyCharm adds a new node with the path to the chosen package.json file on its title and builds a scripts tree under the new node.
To re-build a tree
Switch to the required node and click on the toolbar.
To sort the scripts in a tree by their names
Click on the toolbar, choose Sort by from the menu, and then choose Name. By default, a tree shows the scripts in the order in which they are defined in package.json (option Definition order).
To run one script
Double-click the script.
Select the script in the tree and press Enter or choose Run <script name> from the context menu.
To run several scripts
Use the multiselect mode: hold Shift (for adjacent items) or Ctrl (for non-adjacent items) keys and select the required scripts, then choose Run or Debug from the context menu of the selection.
Toolbar
Add package.json
Click this button to have a tree of scripts for another package.json file built. Choose the required package.json file from the list. PyCharm adds a new node and builds a tree of scripts under it.
Remove package.json
Click this button to remove the tree of scripts under the selected node.
Reload scripts
Click this button to have the tree of scripts under the selected node re-built. You may need a tree re-built after updating the corresponding package.json file because npm does not apply changes to trees on the fly.
Collapse all
Click this button to hide all the scripts trees and have only package.json nodes displayed.
Click this button to configure the current view and to change the viewing modes of the tool window, see Tool window view modes for details.
Note that most of the menu items are options that you can turn on or off. An option which is on has a check mark to the left of its name. The npm -specific options are:
Sort by: select this option to configure the order in which scripts are shown in trees. Click on the toolbar, choose Sort by from the menu, and then choose Name. By default, a tree shows the scripts in the order in which they are defined in package.json (option Definition order).
Hide
Click this button to hide the tool window. To have it displayed again, choose View | Tool Windows | npm on the main menu. The tool window appears again showing all the previously built trees of tasks.
Context Menu of a Tree
npm Settings
Choose this menu item to open the npm Settings dialog and view or edit the Node.js configuration
Jump to Source
Choose this menu item to open the package.json file for which the current tree is built.
Reload scripts
Choose this menu item to have the tree of scripts under the selected node re-built.
Copy Path
Choose this menu item to save the path to the package.json file according to which the current tree was built to the clipboard.
Remove package.json
Choose this menu item to remove the tree of scripts under the selected node.
Context Menu of a Script
Run <script name>
Choose this menu item to run the selected script.
Edit <script name> settings
Choose this menu item to open the Run/Debug Configuration dialog box and edit the predefined settings for the selected script.
Jump to Source
Choose this menu item to open the package.json file for which the current tree is built and navigate to the definition of the selected script.
on the toolbar and choose the required package.json file from the list. By default, PyCharm shows the package.json file in the root of your project. If you have another package.json file, click Choose package.json and select the package.json file you need in the dialog that opens. PyCharm adds a new node with the path to the chosen package.json file on its title and builds a scripts tree under the new node.
on the toolbar.
on the toolbar, choose Sort by from the menu, and then choose Name. 
