What is the maximum graphics card length and CPU cooler height supported by this case?

The case supports a maximum GPU length of 450 mm and a maximum CPU cooler height of 175 mm.

How many expansion slots does this case have for graphics cards or other add-in cards?

This case has 9 expansion slots, and the description notes support for multi-GPUs including four dual-slot cards.

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CORSAIR FRAME 5000D Workstation Case Modular Mid-Tower - Modular Design - Dual 200mm RS Fans - Sound Dampening - 9 PCI Slots - Black

Supports SSI-EEB/CEB and the latest reverse-connection motherboards
Steel side panels with sound dampening materials for quiet computing
A 3D Y-Pattern front airflow panel is optimized for high airflow and minimal restrictions.
A total of 9 PCI slots for multi-GPUs including four dual-slot cards
Large 200mm intake fans for powerful, low-noise cooling
CORSAIR InfiniRail™ Fan Mounting System for unmatched cooling flexibility
420mm radiator support in the roof for high-powered, quiet cooling
360mm radiator support with three mounting locations
Included drive trays for 2x 3.5" hard drives or 6x 2.5" SSDs
GPU immobilization for shipping and anti-sag arm for GPU support