Bitrix: how to form a filter that returns an array of properties of elements bound to the current one?

Question

1C-Bitrix

There is a certain infoblock element, to which several more elements of the same type are linked through multiple selection. It is necessary to form a filter so that GetList would return the data of all bound elements and the current element.
De facto, the situation is as follows - there is an information block of the event catalog, and when a new event is created, past events are attached to it through the element properties, so that reviews of past events are displayed in the reviews section of the new event (reviews are made through the forum.topic component).

Answer 1

Better to make two requests. Firstly, I'm not sure that such a filter can be formed in principle, and secondly, even if it does, the final query will be terribly suboptimal.

Answer 2

Как я понял у вас элементы инфоблока так подвязаны один к другому. Ну что сказать - не надо так делать. Это неверное архитектурное решение. Любое его развитие создаст еще целую гамму проблем.
Используйте для объединения похожих мероприятий теги. Они как раз для этого.