please have a look at your GUI user settings (schedulix!Web Users in the main menu).
There is an option: Enable Batch In Folder Convention Support
If that option is switched off, the "Add as a Child" won't ever show up.
In fact, if you have this option switched on and you choose to create a batch, the GUI will ask you if it should create the folder as well.
This convention arose many years ago in a huge data warehouse environment.
They have huge job flows consisting of thousands of jobs. The convention simplifies understanding the role of a job just by looking at the full qualified name.
We definitely didn't remove that in 2.8.
But we also don't make rules (if possible). Anyone is entitled to use the system she/he thinks is best for her/him.
Anyway, please check the setting. And if it's turned on, please advise and we'll investigate the matter further.
PS: To add those 3 jobs as children to your batch, open the Tab Children, then click the selector button (2 squares and an arrow).
A new window/tab will open. Now copy the 3 jobs, close the new window (if it didn't automatically close on copy) and hit the paste button.