Baldur’s Gate 3 – How to Preview Dyed Items

To do this I am using the Camp Chest.

If you right click an item in your inventory you can select 'Send to Camp'. On PC, you can also use Shift or Ctrl + LMB to multi-select.

This will place it inside the chest in your camp.

Then when you visit camp you can retrieve it from the chest and pass it to whomever you need. So I tend to dump everything my party are not actively using into the chest, and then my new party can go select what items they might need for the next adventure.

I do not know of a way to see a companions inventory without having them in the party.

The spell used to summon Scratch is Find Familiar!

Generally speaking, there are two factors at play here: concentration, and spell uniqueness.

The interactions with Concentration are straightforward -- you can't concentrate on two spells, so two spells that summon creatures and require concentration can never exist simultaneously (at least, not from the same caster!).

This means you can't cast "Conjure Woodland Being" multiple times in order to fill the tactical grid with critters.

The other major interaction is Spell Uniqueness -- you can't benefit from the same spell more than once. This is why Scratch disappears -- you've replaced the previous "Find Familiar: Scratch" spell with "Find Familiar: Crab" (or what have you) -- same as if you cast the spell while your current familiar still exists.

I suppose one final variable is duration -- for instance, Spiritual Weapon lasts 10 turns, whereas Animate Dead lasts indefinitely (or until a long rest, at least). If the duration is too short, you'll find it harder to get overlapping summons.