Ask HN: Enhancement Proposals for Engineering Teams?

I'm currently evolving my team's process and wearing half a product management hat until our startup gets its own organization for that.

We have two PM boards. One for high-level product roadmap with goal and feature-level card titles and checklists for business requirements, and target delivery dates. Another board for technical work that follows a different Kanban-ish flow to limit work in progress (todo, research, prototype, test, deploy, monitor, release etc.).

In trying to capture the rationale for various designs, tooling, and architecture choices, I've mostly been writing comments and notes in the cards directly, or just making decisions behind the scenes and implementing straight away.

I'd like to have some more durable reference for design decisions to make sure we are always considering alternatives, tradeoffs, and utilizing skills and experience, rather than rushing under pressure from the business or adopting over-complicated abstractions that future selves/colleagues will pay the price for.

Has anyone used a PEP-like process for technical designs outside of community projects?