To create and manage custom email templates in Google Workspace, you can follow these steps:

1. Open your Gmail account and click on the gear icon in the upper right corner.
2. Select "See all settings" from the dropdown menu.
3. Click on the "Advanced" tab.
4. Find the "Templates" section and click on "Enable" if it's not already enabled.
5. Click on "Save Changes" at the bottom of the page.
6. Compose a new email and enter the content you want to save as a template.
7. Click on the three dots in the lower right corner of the compose window and select "Templates".
8. Click on "Save draft as template" and then select "Save as new template".
9. Give your template a name and save it.

To use a saved template:

1. Open a new compose window.
2. Click on the three dots in the lower right corner and select "Templates".
3. Choose the template you want to use and it will automatically populate the email with the saved content.

To manage your templates:

1. Open your Gmail account and click on the gear icon in the upper right corner.
2. Select "See all settings" from the dropdown menu.
3. Click on the "Advanced" tab.
4. Find the "Templates" section and click on "Manage templates".
5. From here you can edit, delete, or create new templates.