Why can't i edit my photos on iso 18.0? what happened to the edit button?

In the little bar at the bottom of the screen with three icons including a heart, tap the "slider" icon, the rightmost one in that bar.

Regards.

The Photos App has had a major overhaul in iPadOS 18 - changing many aspects of the App and its functions.

The iPad User Guide is a rich (and often overlooked) source of information. Perhaps this section of the updated Guide will provide some useful insight:

Edit photos and videos on iPad - Apple Support