What do you mean woth "periodic" activities ?

I understand what is a periodic meeting, as meetings have a defined date.
Activities don't, so I don't see what periodic activity is.

for example, I would like to book a time slot task of "test" of 2 hours every 1st Monday of the month.

Request recorded as Ticket #1748/
Not sure it will be done soon, as it seems complex compared to benefit (possibly new planning mode is required).

As a workaround, you can use Meeting for this purpose.

As a workaround, you can use Meeting for this purpose.

that's what I'm doing now. 😉