Whew! You made yet another beautiful design for this latest call for testing. Thanks as always for digging in so deeply and highlighting the Outreach Program's efforts.

From a user viewpoint, I feel like my custom-created templates belong to me rather than the theme. I can see a user switching themes after a couple of years and building a dozen or so templates having a poor experience in this situation.

This is an excellent point and I opened an issue here to document the feedback:

https://github.com/WordPress/gutenberg/issues/31954

I welcome anyone to chime in further on the solutions they'd like to see as I can definitely see that leading to a frustrating experience.

One of the more frustrating aspects of the template editor is the lack of space at the bottom of the frame.

I nearly opened an issue for this but stopped upon realizing that this is likely intentional to preserve the WYSIWYG experience, particularly when editing a template vs writing content. I'm not sure what a good solution is here but I'll note this in the summary post for now as a point of frustration. My mind goes straight to this might be necessary frustration in order to preserve the one to one view.

When adding a horizontal Buttons block, there is no space between individual buttons.

Reported in the theme experiments repo: https://github.com/WordPress/theme-experiments/issues/262 Count me in as a big plus 1 to have more control over the buttons block :D

Because neither the Columns nor the inner Column blocks currently have padding controls, the only way for users to “fix” this is to add a background color.

Nice snag. I opened an issue in the theme experiments repo once more but might need to open other issues in the Gutenberg repo depending: https://github.com/WordPress/theme-experiments/issues/263 Work is underway to add more spacing controls to blocks so I imagine this scenario is covered in the long run but will be double checking to make sure.

However, I would have preferred a flow where the content portion of the template was a part of the post and output via the Post Content block.

I mentioned this in the comments of the post but, originally when mapping this out, that was the plan! However, I ended up running into a wild error with the post content block: https://github.com/WordPress/gutenberg/issues/31798 I just replicated it on a brand new test site as well. Generally speaking, I try to be mindful of not sending people in the direction of obvious errors that are well documented with these calls for testing (massive waste of everyone's time). Needless to say, the ultimate call for testing wasn't the original approach I wanted to take.

That sort of moving back and forth between post and template editors may have opened up some more usability hangups that would be worth exploring.

As James mentions above, there's work underway to add in some friction/structure to the experience to make it more intuitive to use. It's unclear if the "click to edit" experience will make it into 5.8 though.