How to make communication succinct and more impactful?

I really like this question as I believe it's pretty broadly applicable among software engineers, and in fact, it's something I've struggled a lot with myself.

First, I recommend the following resources on high-quality technical writing:

• "How can I most effectively talk about my projects?"
• "How to get more visibility on work?"

And here's my advice:

• Always have a tldr; for anything >3 sentences - This is covered in the above resources, but it's such an important point that I just had to have it again. This is especially true if you're doing a broader communication like a project update post in Slack/Teams/Email/Workplace. At a big, cutting edge company like Grab, people are very short on time, so this is very necessary.
• Use your messages as a pointer - As a software engineer, it can be very tempting to go in the weeds and break down everything that's happened. This tactic is a way you can have the best of both words. Let's say you have written a project update post. Just have 4-5 lines covering the progress at a high-level (whether it's on track, what was done in the past sprint, upcoming blockers, etc) and for all the nitty-gritty, you can link a technical spec or a similar document (I always have one of these for any substantial project). This way, the people who only care about the high-level details get their concise update (product managers often fall into this category), and folks who want to dig deeper (e.g. other engineers) can click into the linked resource and read to their heart's content.
• Reduce all your communications in length by 50% - This is just an arbitrary goal I've thrown out there, but I've generally seen it work in these situations. Whenever you write something, take the initial length and try to divide it by 2, either through eye-balling or using a word count tool.
• Always have organization - Bullet points are a great start, but I also like bolding/italicizing core points and having clear sections with headers/title. You'll see me do this all the time with my Q&A responses here on Taro 😀 Length is definitely a factor, but perception of length matters a lot too (and is maybe even more important). Even if something is just 1 paragraph, if it has no bolding/bullet points/section, it can feel super long.
• Thank the reader for anything long - As mentioned above, perception is important, and this is another way to help with it: If something is long, people are more likely to feel like reading it was a slog (and hence give you feedback about it) if you aren't appreciative of their effort. Expressing your gratitude is a way to ameliorate that "slog" feeling - You can do this by adding a simple, "Thanks to everyone who took the time to read this!" to any lengthy post/message you write. I highly recommend my video about the power of thanks to learn more about this as well: Effective Communication Guide [Part 3.1] - The Power Of Thanks

Here is how I may restate this question:

My slack messages are too long.
How can I shorten them while retaining detail for PMs?
The only feedback my manager gives me is "Keep it short!"
I now review my messages, but would like to improve.

Often I find value in omission. If somebody wants to know more, they ask.

You say that you find a need to explain yourself in detail, and that may be root of the issue. It's not about your needs, it's about the needs of the person asking you the question. Imagine yourself in the other person's shoes, and tailor your message to that audience. The succinctness will naturally follow.

Here's a few things worth investigating further:

• Post an example of something your wrote and ask for feedback from others, ideally outside of your work for a fresh POV - happy to weigh in again if you post something for us to critique.
• "Short" is likely a proxy for "relevant and precise". Strive for the latter and it will be the right length
• Organize information in a coherent hierarchy. Look at an example of "Minto's pyramid". Layout the structure for people ahead of time, then proceed sequentially through each branch of the pyramid
• Use an Appendix or links to abstract away unnecessary detail. Give the minimum amount to solve the problem, often leading with the solution, then explaining rationale/details as supplementary content
• Don't be afraid to cut things out. I often struggle with this as well since I get attached to the content even though it some of the weaker points dilutes the stronger ones.

I have had the same feedback in a prior role.

One audio book I found helpful to me for keeping it short and getting to the point is "Pitch Perfect" by Bill McGowen.

https://www.audible.com/pd/B00IA23AUM

Sometimes I tend to use ChatGPT to improve my messages, specially given English is not my first language. It often times makes it more simpler and easier to read. You can also ask it to improve formatting.

PS: You can do something similar but please make sure not to add any sensitive/personal info while asking ChatGPT to improve it

When I need to communicate something that is difficult to put into words, I follow this recipe:

1. What question(s) am I looking to answer?
2. Why are is it important to answer?
3. Break the question(s) down to smaller bite-sized pieces.
4. Answer each sub question using simple words.
5. What would someone who disagrees say? What's your rebuttal?

This is exercises clears the mental clutter of your mind and organizes your earned secrets into a simple, digestible explanation that you can use in design docs, PR descriptions, explaining why you're facing a blocker if pressed during standup, 1:1's where you need to give critical feedback and chatting with XFN partners.