Unique visitors not showing up for other periods but "day" and gets removed in the custom report plugin

Yes I’ve followed https://matomo.org/faq/how-to/faq_113/ and yes I’ve invalidated the historical data.
And I’ve tried this trick of adding the website suggested by: https://matomo.org/faq/custom-reports/how-do-i-see-the-total-number-of-visits-or-unique-visitors-for-each-website-in-a-custom-report/

And I’ve also added unique user IDs as we’re using user IDs for tracking this intraweb. We need the number in order to track how many user have read an article as that will tell us how many employees have read important information. Is this feature possible in Matomo? If not can someone advise us on a product similar to Matomo but where this feature actually exists?

Hi @Feldon
As this concerns Custom Reports premium feature, I let @innocraft give an answer.
On custom dimension, it seems something is also a missing:

Hello @Feldon Thank you for reaching out to us. Since this is a query about Premium plugin, please reach out to us at shop@matomo.org so we can investigate on this further. Thank you for using our plugin.