There are 2 ways to do this:
1. You could do it the proper way and record each trustee as owning shares.
We have written a article on how pensions (e.g. SIPPs and SSASes) should be recorded as shareholders:
Exactly the same principle applies to EBTs. You can record up to 10 trustees as joint shareholders. To create a joint share holder see below:
How do I create a joint shareholder?
2. You could simply register the name of the EBT as a corporate shareholder. When asked for the company number just enter '00000000' or 'n/a' Please see How Do I Allot Shares to a Corporate?