I agree that I was disappointed by not being able to inactive accounts in a batch in QB online.  But, I found a way to make it go a little faster by not having it send me back to the top every time.

Print the Chart of accounts

Type the account name that you want to inactive in the "Filter by name" box at the top

Then it creates a short list and eliminates scrolling and searching

Also subaccounts are in-actived when their top account is in-actived,

Worked out well for me!