L’origine des pantographes :

Un premier bras est fixe par rapport au support, le bras central est prolongé par un petit pointeur, et le dernier est muni d'un crayon. En déplaçant le pointeur sur le diagramme, une copie du diagramme est réalisée par le crayon sur une autre feuille de papier.
https://fr.wikipedia.org/wiki/Pantographe_(dessin)

Sculptors use a three-dimensional version of the pantograph,[5] usually a large boom connected to a fixed point at one end, bearing two rotating pointing needles at arbitrary points along this boom.
https://en.wikipedia.org/wiki/Pantograph

Now to constructions:

Featuring a hydraulic self-climbing system, the placing boom is able to climb up alongside the lift shaft in the building with the rise of floor levels. The vertical reach of the placing boom relies on the performance of your concrete pump.
2 Length of booms (m)
3 Articulation of booms (°) …
https://www.cabrm.com/self-climbing-placing-boom-elevator-fi...

Freightliner M2 112 Boom / Bucket Truck - 2013 Altec AH125 Aerial Lift, Automatic
Category Boom & Bucket Trucks

https://www.mylittlesalesman.com/freightliner-m2-112-boom-bu...

Platform Elevator Saves Time and Frustration for Operators
:
It’s a common problem in crowded areas. An operator maneuvers up to the worksite, only to stop work and reposition the boom—or sometimes worse, the truck—to reach more challenging areas required of the job. In congested work areas where space is limited, time spent repositioning while minding the boom, the knuckle, potential traffic hazards and other constraints can add up quickly, causing lost time and frustrated operators.
With the 24-inch platform elevator, operators can reduce the time they spend readjusting the boom or truck. The elevator allows operators to move the platform up to 24 inches in a vertical plane without moving the boom, saving valuable time and frustration. The elevators also allow operators to approach the worksite at different angles and helps them reach the back side of a pole when necessary, increasing their range of work within this environment.
https://www.altec.com/platform-elevator-saves-time-and-frust...

A boom lift comprises a platform or bucket at the end of a hydraulically controlled extended arm that is attached to a grounded base. The arms hydraulic control allows it to extend both horizontally and vertically to carry people, materials and tools to extended heights.
:
There are two common types of boom lifts articulating and telescopic.
1. Telescopic boom lifts sometimes referred to as straight or stick boom lifts, feature a single hinged extendable arm that can stretch over distance.
2. Articulating boom lifts sometimes called knuckle booms from the knuckle like connectors that connect the multiple arms that provide the unit its reach ability.
https://www.adaptalift.com.au/blog/what-is-a-boom-lift

The Genie® Z®-30/20 N articulating boom lift offers quiet, emission-free operation in the most sensitive work environments. With this Genie® narrow electric lift, operators can easily drive through standard doorways, work close to buildings or around obstacles, and access overhead work from aisles and other congested areas.
https://www.genielift.com/en/aerial-lift/articulated-boom-li...

--------------------------------------------------
Note added at 3 Tage 23 Stunden (2023-08-22 12:24:13 GMT)
--------------------------------------------------

Now I looked into Althea’s link and found the following:

• Les modèles équipés d’un bras pendulaire fournissent une plage de fonctionnement supplémentaire. (p. 6)
• Le bras pendulaire permet une plage de fonctionnement accrue (p. 7)
Toutes nos nacelles à flèche télescopique sont disponibles avec ou sans bras pendulaire, tandis que toutes nos nacelles articulées sont munies d’un bras pendulaire de série
• Le bras pendulaire peut pivoter avec précision jusque-là où vous devez travailler. (p. 12) …
https://www.skyjack.com/sites/default/files/specifications/B...

Then I searched the relevant operating manual for type SJ85 AJ Articulating booms:

Boom
▪ Ensure there are no loose or missing parts and there is no visible damage.
▪ Ensure all bolts and pins are properly tightened.
▪ Ensure all hoses are properly tightened and there is no evidence of hydraulic leakage. (p. 47)

NOTE
To perform this function test, ensure there is sufficient space to fully raise and extend boom. (p.54)

6.2-1 Platform uphill
If the MEWP becomes tilted with the platform uphill (refer to Figure 25) follow the steps below to return to a lowered and retracted position.
1. Lower main boom completely.
2. Lower riser completely.
3. Retract fly boom completely.
4. Drive to a firm, level surface. (p. 68)
https://techpub.skyjack.com/document/?type=manual&id=4420