Hello.
Then a skill from main skill tree is also useable with the awakening weapon - it would be written in the description - that doesn't appear for spellbound.
I just know that Fissure Wave has mana regeneration in the awakening but i just use my witch as Karanda Char so i can't tell if there is more.
You can put mana regeneration per hit also as Skill Add On on one of your skills - but in the end most classes will go for endgame also for the infinity mana pot.

I recommend you to join the Witch Discord to get more Informations! They have also Skill Combo listed and which Add Ons are useful to use.
https://discord.gg/zNWeZ8v

Also here a link to the Infinity Potion Guide
https://www.blackdesertfoundry.com/infinite-potions-guide/

Thanks I have put mana on hit on all my addpn skills and as second addon something the discord suggested, I can now sustain mana when fighting groups :)

Awakened witch was recently changed to have the mana gain from spellbound heart, from having a pet summoned. you can check this by looking at Summon Gorr or Tett. Spellbound heart will cancel when swapping into awakening due to this change.