Most Jira teams also run Confluence for specs, meeting notes and diagrams. That means two products, two bills, two permission models and a lot of links between them. Starlex keeps documents inside each project.
Notes that do the job
Each project has Notes with rich text, headings, checklists, tables, callouts, collapsible sections, code blocks and LaTeX maths. Autosave and conflict recovery mean two people editing the same page do not overwrite each other.
Diagrams without a plugin
A draw.io style editor with over a hundred shapes, connectors that route around shapes, pages, layers and templates. Import Mermaid or draw.io files, export them again, and embed any diagram in an issue or note.
One place to find it all
The Docs hub lists notes, whiteboards and diagrams across every project you can see, so nobody has to remember which space a page lives in.
Same people, same permissions
A note belongs to its project, so whoever can see the project can see its documents. No separate space permissions to keep in sync.