I have been making progress towards meeting senior level competencies. My manager is aligned and wants to put me up for promo at the end of the year. However, I’m looking for a third project in Q4 to really nail down my case. Additionally, I want to provide more impact and learn how to define new initiatives. I love creating “swim lanes” for my teammates and leading projects that grow their scope. How would you recommend:
I have a lot of ideas for step 1, but am struggling to choose which are appropriate to pursue. Previously, I built a reusable web component at a company wide scale, and am working with a cross org team who wants to use it. I am also working on a technically complex web authentication project that has potential to be used by other teams. Both of these project were scoped by me (with some guidance from my staff mentor) and my manager has communicated they are senior level projects. I have built good relationships with my teammates, our direct stakeholders, and several cross-org engineers. I’m also exceeding expectations at my current level, so there isn’t anything to worry about there. However, I feel like I’m hitting a wall and need to figure out the next project that will turn my promo case into a slam dunk. Any advice? I’m a frontend web engineer if that helps. :)
Coming up with a project idea
I recommend this: "How do I come up with innovative, impactful ideas and bring them to my team?"
After you get the idea, you need to do the exercise of estimating impact and necessary time spend to accomplish the project. It's awesome you have a Staff Engineer mentor - Make sure to consult them and your manager.
Vetting the project to make sure it has enough scope for a senior level (or staff! I would love to provide more impact)
Measuring scope is hard as it's definitely not math and a lot of it is subjective, but I did my best to turn it into math here: https://www.jointaro.com/course/grow-from-mid-level-to-senior-senior-l4-to-l5/at-a-glance-mid-level-vs-senior/
Vetting the project to make sure it has enough impact for a senior level
Impact and scope are sort of similar (I consider impact a sub-set of scope actually). I highly recommend going through the project credit section of my overall promotion course, which you can start from this lesson: https://www.jointaro.com/course/nail-your-promotion-as-a-software-engineer/its-not-just-about-impact/
For what it's worth, both the projects you mentioned seem like senior-level projects to me, provided that you have high enough quality execution. The web design component task is a classic senior+ promotion project (the tricky part is convincing other teams to buy-in instead of being lazy and continuing to do things the janky ad-hoc way).
Keep in mind that you don't have to come up with something entirely novel for the project idea. You can just extend successful projects to get more impact.
In fact, this is the standard way to get more impact, since there's almost always more "juice to squeeze out of the lemon." This is much lower risk than a brand-new initiative.