Creating checkbox in rich text field via scripting

[Fosamoa]

Checking for a completed 'checkbox' field seems pretty straight forward but for my purposes I have multiple tasks per individual entry (via rich text formatting in a long text field). Can I create a formula to automate checking individual checkboxes within a single cell, and then update the record accordingly? 

[TheTimeSavingCo]

Kind of.  The ticked checkboxes are technically "[x]", so you could use a formula to check for that.  Could you provide some example data as well as what you would like to happen?

[Fosamoa]

Thanks for replying. I have individual patients with corresponding long text fields containing a checklist of action items. Once an action item is checked as completed, I want to have it move to a 'historical action items' column. 

I have created a formula checking for checked boxes, but this results in all the the items moving once only a single one is checked. Is it possible to specify to look at checked boxes and ONLY move those items while leaving unchecked items in the original column?

[TheTimeSavingCo]

Hmm....yeah this is doable.  I would:
1. Use a formula field with REGEX_EXTRACT() to grab the line where the checkbox was marked
2. Use a formula field to display the same checklist without that extracted line with a SUBSTITUTE()

Then I'd use an automation to:
1. Add that value from the formula field from step 1 above to the "Historical Action Items"
2. Update the original checklist field with that updated checklist from step 2