Player using own Compendium in my game

It seems like this will probably a Yes, but I have no way to test this with my friends at the moment (as they own no books). If a players has made a character race / spells using WOTC books that are not in my Compendium (e.g. Volo's & Tasha's) And I am allowing players to bring in their own character sheets for the game. Will I be able to pull up the relevant Race / Spells details from the character sheet ? Would those same detail then be searchable in the Compendium Seachbar for me /other players ?

The first one, yes, and the second one, no. Anything entered on the sheet is on the sheet. Traits & other information is saved as part of the character sheet, it is not a link to Compendium content. So importing character sheets will not give you access to any extra content in the Compendium. Again, it's all on the character sheet once it's entered. If a player is not the creator of the game and owns extra Compendium content, they are the only one who can access it. Also worth noting is that they will not be able to access their own content if you have disabled sharing for that book in the game settings. Again, it will not have any effect on their character sheet, only Compendium access.

Thanks Oosh, that makes sense.