@MORITZ

You have to edit CommandBar.htm and add this line:

<script type="text/javascript" src="customui/CustomInit.js">

Scroll through the file and search for this block:

<vcenter>
<moi:StateButton
binding="value = moi.drawingAids.objectSnap"
menu="ObjectSnapMenu.htm">
<moi:Text textid="Object Snap">
</moi:StateButton>
</vcenter>

<moi:Spacer>

Add the above line immediately after <moi:Spacer>