Which is a good tool to share software documentation?

I have a very complex software, created by my company's team of developers. The software has both a UI, an editor and a console to run JavaScript and SQL code directly. New features of the software come out every month, changing its core (written in C++) and introducing new options for the end user.

We currently have a user manual with more than 2000 files. These are files written in Markdown and images of the user interface. In addition to the more technical part, the manual also includes more theoretical sections, where the software's operating logic is explained.

We would like to find software to make this documentation (our manual) more usable. Our priorities are:

to have a very advanced and precise search function that can search through the files available to us

have the possibility of inserting multimedia content (videos, images)

have the possibility of quickly editing the manual

make the manual visible only to certain users (via login). Each user can only see certain sections of the manual

What software or tools allow manuals of this type to be managed? Which ones are most commonly used? What do you recommend using in this case?

Thank you!