Starting with Notes 8 (Standard Client) it was no longer possible to select several documents in the Notes inbox with the space bar. You had to use the Windows "standard" way using Ctrl key and mouse.
Some Notes users (including me :-)) missed this feature a lot. For any users who did not realize it yet: With Notes 8.5 it is now back.
You can enable this setting by checking "Preferences -> Basic Notes Client Configuration -> Additional Options -> Show check marks in margin for selected documents".
Oliver Regelmann just corrected me: This options was already introduced in Notes 8.0.2. Thanks!