You can choose where to display the attribute list panel - according to your screen environment:
1)
At the bottom of the LEX window below the tree view panel and the object list panel:
2) At the right side next to the object list:
You can switch between the two positions. Use the Toggle attribute list placement
(right side/bottom) button or
just move the mouse to the edge of the LEX window and wait for half a second - buttons with an
arrow appears which gives you the possibility to re-position the attribute list: