Steps to reproduce:

1. Login to back office.
2. Go to Content / Content structure.
3. Click on "Create" button on the right side menu.
4. After create menu is expanded, scroll down to select a content from the bottom.

Actual result:

See attachment and watch gif please.

Link: https://recordit.co/meOuqly1Yg

User cannot select a content placed at the bottom of create menu because list of content cannot be scrolled down.

Expected result:

User should be able to select every content available in create menu and also scroll menu at the bottom.