How can I combine multiple iOS Apps

There’s no particular tool or mechanism to “compress” eight apps into one. You get to do the integration work. Some (many?) parts of the eight apps can likely be re-used, but the navigation among the eight and the main navigation will likely have to be re-worked.

As an alternative, the eight apps can potentially be configured as part of a group of apps and share storage and files, if that’s what you're envisioning.

diojen wrote:

Thank you for your comment, I am already aware that it is not a tool.

I want to add new pages to the main application and integrate the feature in the other 7 applications. How can I achieve this?

You’re basically asking how a chef can transition from serving seven separate meals into serving a seven-course dinner. As the chef, you determine a serving sequence of the seven courses, probably reduce the portion sizes of each course, maybe remove or rework individual meal elements that might be problematic or irrelevant in the new seven-course plan, prepare and stage the extra plates and utensils and cookware and ingredients needed, sequence and stage the meal preparation, seat your guests, and serve it all.

Design your UI and UI sequencing and determine your shared data if any and these among many other details involved in converting seven apps into one, and then open Xcode, create a new app, manually merge the source code from the seven apps to fit your design, deconflict the code as needed, and rework or rebuild the UI for your new seven-part aggregate app.

TL;DR: There’s no single roadmap for your question. Outside of an app group, apps just don’t chain around.

First, prepare a new app with the UI that you want, then add the code from the other apps, coalescing common functions as you go. There is no magic, you just have to turn the crank.