How to add sub-unit under normal unit?

Hello! My current curriculum looks something like this: Section 1: Punctuation

• Unit: Commas
• Unit: Colons
• Unit: Dashes

Section 2: Grammar

• Unit: Verbs
• Unit: Pronouns
• Unit: Parallelism

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However, I would like to have "sub-units" beneath the units. Something like this: Section 2: Grammar

• Unit: Verbs
  • Sub-unit: Verb form
  • Sub-unit: Present tense
  • Sub-unit: Simple past tense
  • Sub-unit: Present perfect tense
• Unit: Pronouns
  • Sub-unit: Ambiguous pronoun
  • Sub-unit: Implied antecedent
  • Sub-unit: Relative pronouns
• Unit: Parallelism
  • List parallelism
  • PB&J parallelism

Then, under the "Course Curriculum," can you make an accordion style expansion to hide/expand these sub-units? Just like normal units can be hidden/expanded, I'd love for these sub-units to be hidden/expanded when people click on the + or - sign. Is this possible? Thank you!