I think it may be worth discussing and exploring the transform options for template parts. Currently the transform menu includes options to transform template parts in to Columns or Group blocks:

However, neither of this options work. Selecting one just kicks you back to the wp-admin Dashboard 🐛

Should it be possible to transform template parts into other, non-template-part blocks at all? This seems like a potentially dangerous operation that might be better left to the "Detach blocks from template part" option in the ellipsis menu:

One transformation that should be possible in one way or another is switching template part variations. In previous issues the following design has been posited as an option to do this:

Closely related – in #28737 we are exploring how patterns that are contextually relevant to the selected template might be exposed via the transform menu.

Finally, in #27397 (comment) @mtias questioned whether it should be possible to quickly/easily wrap a template part inside another block. As @jasmussen mentioned, this could be useful for things like Sidebar template parts. My personal feeling is that this could possibly be better handled by the aforementioned patterns flow, as it is not a transform in the traditional sense, but it is worth discussing.

Tentative action plan

• Remove Group/Columns transform options on Template Part block – Template part: Remove transform options #29296
• Add Template Part Switching
• Provide a way to view block patterns that are contextually relevant to the selected Template Part – Semantic Patterns #28737
• Potentially create an affordance for template parts to be wrapped in other blocks