Does Glimmer of Light Stack?

It is not uncommon as a glimmer of light paladin to end a fight with large amounts of mana overall. In this scenario you will generally get a fairly low amount of stacks overall and you shouldn't worry too much about "optimizing" your stacks.

Does Judgement of light stack Shadowlands?

Judgments of Light will not interact with each other if several from different Paladins are placed on a single target. Each will heal any ally that hits the debuffed enemy, for the amount of healing appropriate to each Paladin, being sourced from each expected Paladin.

Can Judgement of light stack?

You can use any Judgement with any Seal active. But the healing effects will stack if you use both Judgement and Seal of Light.