It has these features:

Variable Snippets: Extract the changing parts of a long incantation as variables using "{{}}", and then you only need to fill in the variables.

Convenient Input: Simply type "/" in any input field on a webpage to bring up the snippets panel.

No Login Required: All data is stored in Chrome and not submitted anywhere else.

For example, the prompt I often use to summarize text can be transformed into a variable snippet: Summarize the text in {{number}} words: {{text}}

PromptSnippets is currently in the BETA phase, and your feedback is welcome!