Hit > shift + command + p and type snippets
Select Preferences: Open User Snippets
Choose the language type for which you want to add the custom snippet
vscode has comments to explain on how to add a snippet, as described on :> vsdoc
Lets say, we want to open custom snippets for the language GO. Then we can do:

Hit > command + p
Type: go.json + enter And you land on the custom snippet page
Snippets are defined in a JSON format and stored in a per user (languageId).json file. For example, Markdown snippets go in a markdown.json file.

Update new tools:
Snippet generator site: https://snippet-generator.app/