Just use "normal" linked items.
We cannot add all projeqtor items in the meeting.

Ok, but it is not very usefull.

Risks and Problems are Steering items, just as Decisions, Questions or Actions.

It would be great to have Problems and Risks in the Meetin screen.

Yes, this is usefull for one king of meeting.
Deliveries, Deliverables and Incomings may also be usefull.
For other kind of meetings, othe ritems may be usefull (financial items for financial meetings, HR items for HR meetings)
We cannot add all items.

You're right.

It would be great anyway to access those items directly from the meeting session, maybe from some links or search panel or anything else ?

Just in order to stay in the meeting session while creating or linking some of those items.

It's exactly hat the "Links" section is designed for...
... and this gets right back to my forst answer.

I usually use a second (or third) tab/window where i am able to hop to any other point of ProjeQtOr at the same time so that necessary linking can be done

Yes, that is what I also do 🙂