A shelf attached to a shower panel may look light, but it becomes part of the glass assembly. Bottles, water, cleaning and accidental impact all add load, so the shelf and its support should be specified before the panel is manufactured.
The glass needs the right support
The shelf may require clamps, brackets, holes or a dedicated support detail. These must suit the glass thickness and stay away from vulnerable edges. A shelf cannot be safely improvised by drilling a finished toughened panel.
Water and residue collect there
The shelf should drain or be easy to wipe. Its position should not create a ledge where soap, hair and mineral deposits remain against the glass or wall.
Check the bottle height
The usable shelf should fit the products the household actually uses, while remaining clear of the user’s shoulders, the shower door and any controls. A narrow shelf placed too high can become decorative rather than useful.
Compare with a built-in niche
A properly waterproofed niche may provide more stable storage and keep the glass clear. A glass shelf can be preferable where the wall cannot be recessed, but it should be chosen for a reason and recorded as part of the enclosure specification.
Read about waterproofing shower niches and benches, or see why large shower panels have support limits.