In order to add value, you need to first consider the priorities of the business and the leadership team. You could be doing some pretty great work, but if it doesn't advance the business's priorities it will likely get wasted. Once you're doing work which aligns to the business goals, its a good idea to set goals on a quarterly basis.
At the end of each quarter or project, put together a summary of the improvements you made, and review it with business leadership. If you have a team be sure you're setting your team up for these opportunities too. Often times these presentations become very long and wordy. Avoid this. A simple deck with key results and objectives should get the job done.
Once you're ready to go to your next job and want to highlight everything you accomplished, you will have all these decks to look back on as a reminder.