Best way to display Comment field

[ComputerHabit2]

I am working on an app that updates a Sharepoint list.   In that list I have a comment field that appends entries.  I have built a workflow to grab the information and display it. 

As far as design though I'm trying to figure out my best approach when displaying it.  If I review what Microsoft has done they have an edit button that allows adding a comment.

I'm trying to figure out how I would do this.  

• How would I get the Workflow to execute when selecting an item from the gallery? 
  Right now I have the Flow wired to a button but I'd like to execute it when I select an item from the gallery.
  
  
• When editing the field I would click a button to add a comment.  I'm not really sure how to approach this field.  The field is HTML and I guess when I click a button to edit I'd change it in some way.  What would be the best approach with this?  I have read about fields having edit mode but I don't know what that would be for an HTML Text box.  Would it convert to a Rich Text Editor field?  Should I be adding a Rich Text Editor object and making it visible on the same screen?
  
  
• Right now I have an Edit Form and a Display Form on the same Screen.  They're both wired to a gallery so when I select an item I see both forms populated.  What is the best option to switch between a Display and Edit form?  Would I create a button and go between two different screens or can I just make them layered on top of each other and make it visible when clicking an 'edit' button?  What's the best approach?
  
  
• In the example screenshot above in Sharepoint the screen flys out from the side.  I'm wanting to replicate that idea if I can.  If anyone has details on how to do that it would be helpful.  Right now I'm guessing that I would somehow put the field there and make it visible and reduce the size of the edit or display form.  Ideas on how that works would be very helpful.
  
  
  

Thanks in advance.  I'm learning and trying to figure out my options.

[ComputerHabit2]

So far I've gotten my Flow to run from the gallery.  I wasn't sure if OnSelect for a gallery meant each item.  So now my Display form shows the Comments.