Notion allows you to import templates from external sources, such as Google Sheets, Airtable, or even .csv files. This can be a useful way to quickly set up new pages or databases based on existing templates or data you already have. Here's how you can import templates from external sources:

1. Importing from Google Sheets: To import templates from Google Sheets, you will first need to export the data from the Google Sheet as a .csv file. Then you can go to Notion, select "Import" from the main menu and select the .csv file you exported. Notion will then convert the data into a new database in Notion, preserving the columns and data.
2. Importing from Airtable: To import templates from Airtable, you will first need to export the data from Airtable as a .csv file. Then you can go to Notion, select "Import" from the main menu and select the .csv file you exported. Notion will then convert the data into a new database in Notion, preserving the columns and data.
3. Importing from other file formats: If you have a template in another format such as .xlsx, .json, or even .md, you can also import them in Notion by using the Import button and selecting the corresponding file format. Notion will parse the data and create a new page or database preserving the formatting as much as possible.
4. Customizing the imported template: Once you've imported the template, you can customize it to suit your needs by adding your own content, editing the layout, and changing the properties of the template.
5. Saving as a custom template: After customizing the template, you can save it as a custom template by clicking the ... icon on the top right corner and select "Save as template". This will save the custom template to your template library, and it will be available for you to use anytime.

By importing templates from external sources, you can quickly set up new pages or databases based on existing templates or data you already have. It can save you time and effort and help to streamline your workflow. Additionally, the ability to customize the imported template, saving it as a custom template, and collaborate with other people makes it an effective tool for working with data and projects.