Get to Web Parts Maintenance Page for a Modern SharePoint Page

Introduction 

 
In the SharePoint Page, we use a web part maintenance page to see the list of web parts present on the page. This is helpful in the case of any error in the web part that causes some issue on the page. In a classic SharePoint page, you can get to the Web part maintenance page by using ?contents=1 as a query string in the page URL. 
 
Please check the existing article on it here. 
 
For the modern SharePoint pages, use ?maintenancemode=true as a query string in the URL to get to the web part maintenance page. You will be able to see the page details and all the Web part details present on that page. 
 
 
 
Please note, the user should have at least Edit permission to open the maintenance page. 

You can perform the following actions in the web part maintenance page:
  1. View the Web part summary and copy the data and manifest information for each web part.
  2. Remove web parts you suspect are causing problems.
  3. Rearrange web parts.
By exploring the manifest information, you can learn details such as:
  1. Where the web part bundle is hosted
  2. Which external scripts are the web part loading and from where(this is useful to see the localization files) 
  3. What version of the SharePoint Framework has the web part been built on
  4. Which components of the SharePoint Framework does the web part use
To delete a web part on the maintenance page, you should click on the edit page button and select the particular web part to delete it.
 
 
 
Even though you can see the edit icon in the maintenance mode, you cannot edit the web part because the web part code is not executed when the user opens it in maintenance mode.