What tool do you use to write software design docs and what don't like about it

I wanted to know what documentation tools are people using to write software design docs. I have mostly seen that people use whichever general purpose Docs application is being used in their organization to write software docs too (Google Docs, Notion, etc).

If there was to exist a documentation software especially for software design documents, what features would be the most important? Are there any tools which do this well?

Also, as a software engineer, have you ever felt that the documentation software you use is lacking and does not help you communicate your ideas well, due to lack of native support for content like diagrams, schemas, state machines, etc.