For organizing and keeping track of launch activities, I created templates that I have carried with me from company to company. They contain all of the best elements from past launches (both my own and other PMMs I have learned from). And frankly, there is nothing fancy about them - they are mostly just spreadsheets! It's not to say that there aren't tools that can help streamline processes - I've seen launches effectively organized in Trello and Asana, for example. But what I like about my collection of self-made templates is that they are easily customizable and flexible to fit my immediate needs. I also feel connected to them, which helps me feel confident in implementing them.
However, as important as templates are to provide a single source of truth, I believe that the real trick to ensuring continual alignment is to find spaces for constant communication. For many PMMs this usually means weekly (or even daily) launch standups. For me, I've found success in ritualizing a weekly "What's Shipping" call with all of the key stakeholders in the org (Product, Sales, Marketing, Success, etc.). This is a standing meeting where we check in on all launches in flight, review the launch plan spreadsheets, perform retros post-launch, and more. If we don't have any launches to talk about, we don't have the meeting. But by creating a constant touchpoint, it builds a habit within the org that we are always thinking about launches. As a result, everyone feels more confident with how launches is progressing and can pass on relevant information to their teams so everyone is in the know.
In short, it's all about constant communication!