Just got an 2002 Chrysler Voyager. I can fold down the rear bench seat using the black lever on it but can't find a lever, or other release device to fold down the middle bench seat. How can this seat be folded to carry oversize cargo?

Remove headrest, there is a small button on the base of the headrest mount you need to push in. Next pull up the strap at the front of the seat cushion bottom, then flip forward. Press in the flipper on the top of the seat back and pull forward.

On each side of the trunk their are levers you pull to release the back seats to be lowered.

To fold-down rear seat on 2007 Chevy Malibu, follow these steps:
1. Open the trunk
2. Pull on one or both the handles located on the upper side of the trunk
3. The handle located on the driver's side will unlatch the bigger part of the read seat
4. The handle on the passenger side will fold down the smaller portion of the rear seat.
5. Once done, you will have a seat that's nicely folded down.

Fold down rear seats in 1995 Pajero 4x4 wagon - Fixya

https://www.fixya.com > cars > t15385582-fold_down_...

May 19, 2017 - Open the back trunk, look near the top of the trunk, and pull the two black levers. They have a seat folding down symbol. That will release the ...

Videos as well

https://www.google.com/search?q=Fold+down+rear+seats+in+1995+Pajero+4x4+wagon

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push back firmly at front of seat at bottomlocating clip released with upward preasure

Trip all three rear latches - the ones that are not tripped prevent the release levers from releasing

The problem:
The set belt stop has been lost so the seat belt retracts too far when the seat is laid flat. When laid flat the release mechanism locks as it should when not level so the seat cannot be raised up as the belt is too tight and locked.
The Solution:
1) Push the two little clips to release and remove the headrests.
Pull the grey lever on the right of the seat base, lift seat base up and forward toward the front seat..
2) See two red capped leversat the back of the two seat hinges and lever them to the upward position, this releases the seat.
Rock the very heavy seat unit upwards and lift complete unit upwards.
3) Take it out of the car and turn 180% so that the back of the seat and base are in the upward position and the seat belt will pull out as it should
4) Replace the missing belt locking stop (I used a tie pin permanently fixed using super glue).
5) Fold seat back down and test then either re-fit seat unit or leave out to decrease fuel consumption..

I am going to assume you mean the normal rear seats, not rear facing seats in the very back.
The rear seat folds down. The benches fold up from the back. When they are up you can see how to easily remove them if you want.
When the benches are up the backs fold down. There are levers on the top the slide forward to release them so they can be folded down. Tip the outboard head restraints forward by pulling their straps. The center head restraint has a button behind its right-hand support that you push to allow it to be lowered.

On W-Body vehicles, the front seats are secured to the floorpan by two front hook attachments and two rear bolts installed to nuts welded to the floorpan.
The manually operated two-way front adjusters provides only fore and aft movement of the seat. When the seat adjuster handle located on the front seat is pulled up, the seat adjusters unlock, permitting travel of the seat. When the seat is in the desired position and the seat adjuster handle is released, the seat locks in place.
A power operated six-way seat adjuster is available. The adjusters are activated by three 12 volt, reversible, permanent magnet motors with a built-in circuit breaker. The motors are energized by a switch bolted on the seat side panel.
The three motors drive the front seat and rear vertical actuators and a horizontal actuator. When the adjusters reach the limit of travel, torque is absorbed through the rubber mounted grommets located between the motor and the support. An overload relay is provided in the circuit and will open should excessive stall be applied.
The optional 60/40 split bench front seats have seat back head restraints on the driver's and passenger's seat back. The head restraints are designed so they cannot be removed from the seat back without first inserting a small rounded tool inside the head restraint support tube to release the locking tab. The 60/40 split bench seat is equipped with a reclining mechanism on both the driver's and passenger's side. The recliner lever is located on the outboard side of the spring cushion. When the lever is pulled upward, the spring loaded dual linear reclining unit located in the cushion frame is released, allowing the seat back to be pushed rearward or allowing the spring loaded reclining unit to bring the seat back forward.
Bucket seats are equipped with manual reclining mechanisms. An optional six-way power seat adjuster is available. Some bucket seats are equipped with inertia seat back locks. This system allows the seat back to fold forward without requiring the occupant to release a locking lever or access to the rear seat area. During a sudden stop or deceleration, or if the front of the vehicle is nose down, the inertia system of the seat back lock will engage, holding the seat back in its rest position. A release lever is provided to allow manual release of the seat back lock when the vehicle is in the nose down position. The release lever is located at the lower rear outboard corner of the seat back.
Some W-Body vehicles (notably Pontiac coupes) have passenger front seats equipped with an E-Z Entry device. This is actuated, in an unoccupied seat, by completely folding the seat back forward disengaging the adjuster, and sliding the front seat forward to gain access to the rear seat area. To return the seat to its normal position, return the seat back to its rest position, and slide the entire seat rearward, engaging the adjuster.
W-Body rear seats are available in several styles including a rear seat with an integral child restraint device.

Try looking for a strap in your trunk it should be located at the upper inside of your trunk, there could be one or two straps, when you pull on these straps they act as a release lever for your rear seats, pull the straps toward you and push the seats forward from the trunk side.