I have the Player's Handbook and a number of add-on bundles, but one of my games is a strict "Player's Handbook only" game. I get in trouble when I add a spell that ends up not being in the core handbook. Is there a way in my character to specify "only show me spells and other content from the Player's Handbook"?

For the moment I am constantly going back and forth every long rest as I rearrange my spells and it's a bit annoying. The simplicity of "I only see the spells I can use in this game" is what I desire.

Am I doomed to manually managing my Druid's spells?

There is no way to limit options to PHB only in the character sheet/builder, at this time.

For spells you can use the Spells search feature in one tab, filtering to PHB only, and have the character sheet in another tab - this way when prepping spells you have a reference to work from.

This is planned (possibly for this year). I also really want this for AL.