One corner can hold both a bed and a scratcher if each remains comfortably usable and the arrangement leaves clear access. Measure the scratcher's complete footprint and the space needed for your cat to stretch, rather than placing it so close that the bed blocks the surface. The bed should not sit where normal scratching movements repeatedly disturb a resting cat. This matters particularly when two cats may use the items at the same time.
Consider stability on the actual floor and whether either item will shift into the other's space. A combined piece of furniture can be practical, but its sleeping area and scratching area should each meet your needs independently. Keep the corner easy to clean and avoid obstructing a door or curtain. If the cat ignores one function, try improving its position before assuming the material or style is unsuitable.
Mark the space needed while the cat scratches, not just the post’s base. If its body would extend across the bed entrance, separate the two pieces enough to keep the resting route open during ordinary scratching.
For product comparisons alongside this advice, see Sisal Pair scratching mats and Paw-Villian cardboard scratcher. The details below explain their sizes and uses.
Further reading: cats.org.uk; rspca.org.uk; cats.org.uk.
Sisal Pair scratching mats
Paw-Villian cardboard scratcher
Scratch Central