The formatted string will still be post processed by config.content.format. An argument could be made that this added layer could instead be added/merged into config.content.format. Chose to not do that since it is more work:

• Add type to the MiniNotify-specification object
• Make MiniNotify.default_format() aware
• Update documentation
• Make sure it does not break existing users configurations

Thanks for the PR!

Adding new option specifically for formatting LSP progress definitely does not fit in 'mini.nvim' design. There is a config.content.format and it should be able to be used for this. If no good way to do this, then I am afraid the only way to do this will be manually overriding vim.lsp.handlers['$/progress'].

Now, the only missing part for a more straightforward adoption is indeed some type of source field for notification. Maybe adding to specification is the right thing to do.

In any case, I'll close this PR and will think a bit more about this. Thanks again for your time!